Count your profit after costs.
The exchange charges a fee when you open and when you close a position. Perpetual futures also have funding — a regular payment you either pay or receive.
Back to our 500 USDT long. If the price rises 2%, the move earns 10 USDT. With an example fee of 0.05% on each side, about 9.50 USDT is left after trading fees.
The same trade — with fees.
Price up 2%
= 9.495 USDT
10 USDT from the price move, 0.25 USDT to enter and 0.255 USDT to exit. The exit fee is charged on 510 USDT.
If the price falls 2%, the result with the same fees is −10.495 USDT. Funding is zero here. The fee rate is an example — check your exchange's terms separately.