There is plenty of evidence of wash trading occurring on Bitfinex and other exchanges - there are also many accusations that the exchanges themselves wash trade, to pump up their own volumes. They don't need to pay their own fees!
Those who are downvoting the parent, please explain why? He is correct. Is the assumption here that the exchanges themselves are wash trading and not charging themselves fees? Seems possible. But otherwise wash trading is very expensive due to the maker/taker fees.
Taker fees are significantly discounted for higher volume traders, because they bring smaller traders to an exchange. I know two mid-sized whales who have almost 0% rate as long as they trade certain number of BTC a month.