Why is my fee bigger on a larger account?

The fee is a percentage of the position size, so a bigger position pays more dollars at the same rate.

The trading fee is a share of the position’s notional value (quantity × price), charged when you open and again when you close. It is not a share of your balance. A $1,000 position and a $100,000 position pay the same rate, but the second pays 100 times the dollars.

Example: $1,000 of margin at 10× is a $10,000 position. A $100,000 account using the same 10× on its whole balance trades a $1,000,000 position, 100 times bigger, so its fee is 100 times bigger in dollars. The rate did not change; the position did.

The rate is the same on every plan and phase, and it is always below the Binance Futures rate for the same order. To pay less in total, trade a smaller notional or fewer round trips, and use resting limit orders where it suits you: a limit that rests and fills later pays the lower maker rate. Your account’s Rules page shows your exact rate next to Binance’s, and the info icon beside any fee figure in the terminal shows the same comparison for that figure.