>What mainly interests me is how much money they are actually making, I suspect it's very profitable.

Well, it's about calculating their site support, storage, server and bandwidth costs. What might those be? Aside from these, I've seen them claim they use volunteers for much of their site support and certainly don't pay, or need to pay, anything for marketing since the word of mouth (partly through notoriety and partly through uniquness coupled with extreme usefulness) is more than enough to keep them famous.