Taker fee
What an exchange charges for removing liquidity with a market order — paid four times in a full arbitrage round trip.
A maker adds liquidity by resting an order in the book and is charged less, sometimes rebated. A taker crosses the spread and pays more. Arbitrage entries are almost always taker orders, because a resting order that does not fill leaves you one-legged and directional.
The arithmetic that decides a trade: two legs in and two legs out means four taker fees. At 0.05% per side that is 0.2% before slippage — so a 0.25% spread is not a 0.25% trade, it is a rounding error with extra steps.
Fee tiers are the quiet edge in this strategy. Volume tiers, exchange tokens and referral discounts move the break-even threshold, and a trader paying 0.02% per side is looking at a meaningfully larger set of viable routes than one paying 0.06%.