Hmmm, I'm surprised noone mentioned the fact that trading fees, most of the time, depends of how you trade.
You have taker and maker fees, and they are different.
A market taker is someone who fills already existing trade orders and doesn't create its own (ie if you "take" an already existing buy order of 0.253 BTC at 7846 $, in fact you sell 0.253 BTC at 7846 $). In this case, trading fees are the highest.
A market maker is someone who creates it own trade orders, and waits for someone to fill them (ie if you "make" a buy order of 0.253 BTC at 7846 $, you are indeed selling 0.253 BTC at 7846 $, and the taker will buy it. In that case, you have the lowest trading fees, and in some exchanges, it's not a fee that you pay, but you earn a little bit of money everytime you are the trade maker. This earning comes is a fraction of the taker fee that the exchange reverse to you. The reason is because you bring liquidities and volume to the market.

In some exchanges, there aren't taker and maker trade fees. No matter you are the maker or the taker, you will pay same fee everytime you trade.