@kyu
I find CoW Swap's "Order Surplus" concept pretty misleading—maybe even deceptive.
When calculating "surplus," CoW Swap compares the final trade execution against the limit price—which is just the minimum amount you're willing to accept (quoted amount * (1 - slippage tolerance)).
Example: you're quoted 10,000 USDC for selling 1 token A, with a 0.5% slippage tolerance. Your minimum buy amount becomes 9,950 USDC. If the trade executes at 9,975 USDC, CoW Swap claims you got a 25 USDC "surplus".
But in reality, you received 25 USDC less than what you were quoted. That's not a win—it's just better than the worst-case fallback. Calling that a "surplus" feels like spin.