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.
First, it's unconfirmed. What exactly does "industry sources" mean? That someone who knows someone who works there said "oh ya we make a billion dollars dude".
Second, it could also mean "gross revenue" in some form.
I don't believe any of this stuff until someone reputable confirms some level of it. Doesn't it seem strange that they made "exactly $1b"? Not $750M, or $1.2B, or $500M, but $1B?
I think the jury is still out.
That would be strange, but the article doesn't say that, it says "over $1 billion".