Why two people swapping the same pair can pay different amounts

05 September 2026

Two people swapping the same pair can pay different amounts because the total cost of a swap is not a single fixed fee but a combination of variable components: the spread, the network fee, and the price impact of the swap itself. Each of these depends on market conditions, the size of the trade, and the timing of the transaction.

The most obvious reason is the spread - the difference between the best available buy and sell prices at any moment. That spread shifts constantly as orders fill and new ones appear. One person might swap when the spread is tight (say 0.1%), another an hour later when it has widened to 0.5% due to low liquidity or sudden volatility. The exchange does not set a single spread for all users; it reflects the real-time state of the order book or liquidity pool.

Network fees vary by the minute. On Ethereum or similar chains, gas prices rise and fall with network congestion. Two swaps executed ten minutes apart can face completely different gas costs. The person who swaps during a quiet period pays less. The person who swaps during a NFT mint or a DeFi frenzy pays more. The exchange passes that cost through directly; it does not smooth it.

Swap size matters greatly. A small swap - say $50 worth of a token - might move the price negligibly. A $50,000 swap of the same pair can push the price several percent against the trader, especially in a shallow pool. That price impact is a cost. It is not a fee the exchange takes; it is the mathematical consequence of removing a large amount from a limited liquidity reserve. Two people swapping the same pair at the same moment will pay different amounts if one trade is ten times larger than the other.

Routing differences add another layer. The exchange may use a middle currency (like USDC or ETH) to complete a cross-chain swap. The cost of that intermediate leg depends on its own liquidity and spread. One user's swap might route through a cheap, deep pool; another's might hit a thin pool because the direct route was temporarily unavailable. The quoted price reflects the route at that instant.

Slippage tolerance also plays a role. Many swaps let you set a maximum acceptable slippage - say 1% or 3%. If the market moves against you during the few seconds it takes to confirm the transaction, a swap with 3% tolerance might execute at a worse price than one with 0.5% tolerance that fails and gets retried. The person with the tighter tolerance often gets a better price, but may also see their swap fail and need to resubmit.

Finally, timing within a volatile market creates large differences. If one person swaps just before a sudden price jump, they get the pre-jump rate. Another swapping seconds later faces a completely different quoted price. The spread itself can double or triple in a single minute during high volatility.

To understand exactly where each cost comes from, read the hub page What a crypto swap actually costs. It breaks down the components and shows how the quoted price differs from what you receive. The key takeaway here is simple: no two swaps are identical because the market is never static. The price you see is a snapshot of conditions that change by the second.

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