If I plan to hold a loan long-term (say, a full year), does that mean I completely don't need to worry about the origination fee and gas fee puzzle pieces?
Not entirely 'don't need to worry' — rather, these two pieces' proportion of overall cost drops significantly, but they're still worth including in the calculation to confirm, rather than directly ignoring. Extending the earlier calculation example — borrowing $10,000 at 5% annual rate with a 0.5% origination fee, if held for a full year, interest cost is roughly $500, and the origination fee remains a fixed $50 — at this point the origination fee's proportion of total cost drops from the vast majority in a short-term scenario to roughly 9%, genuinely becoming a relatively minor cost item, but still not something entirely negligible.
A more accurate mindset adjustment: the longer the borrowing duration, the lower the origination fee and gas fee's 'relative' importance drops, but this doesn't mean these costs 'disappear' — when precisely calculating total cost, you should still include these puzzle pieces. It's just that in a long-term borrowing scenario, you can focus most of your comparison effort on the interest rate difference between different protocols' continuously accrued rates, since this is the variable with the greatest impact on total cost as time stretches out.
How much can the origination fee and gas fee actually differ across different protocols, and is it worth spending time comparing?
Worth it, especially for a user frequently needing to execute short-term, high-frequency borrowing operations, where the difference can be quite significant. On the origination fee side, as covered in an earlier article, some protocols charge no such fee at all, reflecting all costs entirely in continuously accrued interest — this kind of protocol is noticeably more worthwhile for a short-term borrower; even among protocols that do charge an origination fee, the percentage setting across different protocols can vary noticeably (say, ranging anywhere from 0.1% to 1%), and this difference, converted into an absolute amount for a large loan, could differ by several times.
On the gas fee side, the difference mainly comes from which blockchain or layer of network architecture you choose to execute the operation on — the same borrow/repay operation, gas fees when executed on the main chain could be dozens of times higher or even more than when executed on a Layer 2 (the scaling solution covered in an earlier article). If your strategy inherently needs frequent entry and exit from a borrowed position, choosing to operate on a network architecture with relatively cheap gas fees could save a fairly substantial amount accumulated long-term. Comparing these aspects, for a user frequently executing borrowing operations, genuinely is worth spending time specifically verifying — not a detail you can casually overlook.
If I want to execute an arbitrage strategy requiring short-term borrowing, how should I specifically judge whether this loan's total cost will eat into my expected profit?
A more sound approach is first calculating this entire loan's total cost (interest, origination fee, borrow/repay gas fees, and adjustment costs if mid-way adjustment is needed) into a concrete absolute amount, then comparing this absolute amount directly against the absolute profit your strategy expects to earn, rather than separately comparing relative percentages like 'is the interest rate high' or 'is the fee expensive' — since comparing between percentages can easily make you overlook the genuine weight different cost items carry once actually converted into an amount.
In concrete operation, it's worth picking a conservative assumption scenario (say, the strategy's execution taking slightly longer than expected, gas fees running slightly higher than usual) to calculate total cost, rather than estimating using the lowest cost under the most ideal scenario — since an arbitrage opportunity's actual execution process often encounters a longer wait time or higher network congestion than expected. If the total cost calculated under a conservative assumption still comes out noticeably below expected profit, this loan operation's safety margin is fairly ample; if the total cost under a conservative estimate already approaches or exceeds expected profit, it means this strategy's actual feasibility is worth re-assessing, rather than rashly executing only to find profit almost entirely eaten by cost afterward.
Besides these puzzle pieces, are there other easily overlooked factors that actually affect a loan's total cost?
One frequently overlooked factor is the collateral's own opportunity cost — an over-collateralization mechanism requires you to lock in an asset worth more than the borrowed amount as security, and this locked-up collateral can't be deployed toward other investment use during the loan period — a hidden opportunity cost that, while it won't directly show up on any bill, is genuinely an extra cost you bear when choosing to borrow (rather than directly selling the asset to obtain funds). If the collateral asset you originally hold carries a high expected return rate itself, locking it into a lending protocol rather than deploying it another way could represent a fairly substantial opportunity cost, worth considering together when assessing 'borrowing' versus 'directly selling the asset' as two ways to obtain funds.
Another factor worth noting is the potential cost from liquidation risk — if collateral price swings sharply during the loan period, approaching the liquidation threshold, you might need to pay extra gas fees to urgently add margin, or in the worst case genuinely trigger liquidation, paying the extra cost of the liquidation bonus covered in an earlier article. These are probabilistic potential costs, not occurring every time you borrow, but when planning a borrowing strategy, it's worth factoring this kind of tail-risk potential cost into overall consideration too, rather than only calculating the certain cost under the smoothest scenario.
Seeing a lending protocol display a 5% annual interest rate, it's easy to directly take this number and compare it against other options to decide whether to borrow. But the annual interest rate is only one piece of the puzzle within borrowing cost — deciding based purely on this number, especially when planning short-term borrowing, could very well mean missing a cost substantial enough to change your entire decision. This article teaches you how to calculate a loan's genuine total cost clearly.
Interest is a cost continuously accrued based on how long you hold the loan — also the only number most people ever compare when comparing different lending protocols. The calculation is relatively intuitive: borrowed amount multiplied by annual interest rate, then proportionally converted based on how long you expect to hold it — for example, borrowing $10,000 at a 5% annual rate, expected to hold for 3 months, interest cost is roughly $10,000 × 5% × (3/12) = $125.
As covered in an earlier article, some lending protocols charge a fixed-percentage origination fee right at the moment of borrowing, settled the instant the borrowing transaction confirms, not varying based on how long you hold the loan — whether you borrow for an hour or a full year, this fee's absolute amount is exactly the same. This also means this fee's relative impact on short-term borrowing is far larger than on long-term borrowing: the same 0.5% origination fee, borrowing $10,000 means a $50 fixed cost — if you only intend to borrow for 3 days to execute some strategy, that $50 could very likely far exceed the interest you'd accrue over those 3 days.
Both borrowing and repaying are actions requiring submitting an on-chain transaction, and each transaction requires paying a network fee. Though this cost isn't a fee the protocol charges, it's genuine real money you'll actually pay executing this entire borrowing operation — especially during a period of network congestion with spiking gas fees, this cost could get substantially amplified, worth factoring into your total cost calculation, rather than ignoring it as 'an extra expense unrelated to the loan.'
If your borrowing strategy needs mid-way adjustment (such as adding collateral to avoid liquidation, or partial repayment to adjust leverage ratio), these adjustment actions likewise require paying a corresponding network fee — if your strategy's design inherently needs frequent position adjustment, these accumulated mid-way operation costs could add up to a non-trivial amount long-term, worth estimating in advance when planning your strategy.
Say you borrow $10,000 at a 5% annual rate with a 0.5% origination fee, expecting to hold for 3 days, with borrowing and repaying each requiring one network transaction (assuming roughly $5 gas fee each): interest cost roughly $10,000 × 5% × (3/365) ≈ $4.1; origination fee $10,000 × 0.5% = $50; two gas fees totaling roughly $10; total cost roughly $64.1. This example clearly demonstrates that, in a short-term borrowing scenario, the origination fee ($50) far exceeds the continuously accrued interest ($4.1) — if you decided purely based on seeing a 5% annual rate figure, you'd have been entirely unaware that this loan's actual total cost is genuinely dominated by the origination fee.
Next time you assess whether to execute a borrowing operation, build the habit of adding these four puzzle pieces together (interest, origination fee, borrow/repay network fees, and mid-way adjustment costs), then comparing this total cost against the goal you're executing this loan to achieve (such as an arbitrage strategy's expected profit). For long-term borrowing, this habit might just be an extra confirmation step, but for short-term, high-frequency borrowing operations, it helps you avoid the easily overlooked trap of 'the interest rate figure looks low, but because the fixed cost's relative impact gets amplified, the actual total cost isn't worthwhile at all.'