i just did a simple calculation, about 35k bitcoins are traded on GDAX every day. At its current price of $6900 and a trading fee of 0.3%, the exchange puts about $700,000 in its pocket EACH DAY and it is ONLY for bitcoin. After including all other cryptos, this number can go up to more than $2MM. Since the exchange is active 365 days a year, the exchange's annual revenue can reach almost $1bn!!
no matter how the trusted exchange earn, it keeps that they must pay for the whole system manager, security, partners, maintenance and others.
im sure with this transparent transaction, the exchange didn't really get as we expected. also the security is the most vulnerable issue of exchange, keep it is not as simple as we think. keep the security is like keeping their the partners