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".
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.