Exchanges establish their own fees. The fees are different not only between exchanges but sometimes between different trading pairs on the same exchange. Use a free service like Switchain to compare rates between a few different exchanges for each individual transaction.
There are custodial and non-custodial exchanges. Put simply, the first ones hold onto your assets that you leave with them which is what makes it vulnerable. Once it's hacked there's nothing you can do but watch. Non-custodial ones only hold your assets for the time necessary to complete the exchange.
Hope this helped.
Fees is not my problems but how they give good services and solve my transactions problem is more important. Low fees not guarantee they can give us best services but most exchange with difficult rules and high fees can. I will not suggest you to take exchange with high fees but see how they works will much better, replace your money on that will create better transactions.