It is on EC2. I pay about £2500 a month - but the monthly cost is lowered because a lot of the machines are on reserved instances - with a big chunk paid up front (sometimes by the people I work with) ... I usually work for free because I'm not really interested in financial gain but more interested in interesting problems ... but I gotta pay the bills sometimes, and the people I work with are usually more than happy to chip in if I need it :)