Might still not be that much, if earnings through exchange rate gains were also part of their revenue. btc made what? Over 1000% in that year? If they pooled earlier in the year that are huge gains. If it's only from their 1.5% cut, it is really impressive.
Exchanges are literally printing money. I think nearly a million Ether a day was traded on Gdax at the top.
At $1,400 you're talking $1.4bn a day in trading volume, on (at least) half of which they take a 0.3% fee. That's $2.1m a day, just from ETH. Then there's Bitcoin and Litecoin. Bitcoin probably makes a similar amount. And their "simplified" website on which they charge higher fees.
