Many cryptocurrency exchanges use a maker/taker system for determining their trading fees. The percentage of the order amount charged can fluctuate depending on how your order affects the market for future trades. For those who act as makers, by placing limit orders to sell crypto or tokens that dont fill completely, they are contributing to the creation of a market for upcoming trades and often pay lower fees. On the other hand, takers who place orders to buy crypto that fill immediately, take available trades off the market and thus typically pay higher fees as compared to makers.