True, but you can rent something like a state-of-the-art supercomputer from Amazon for fairly reasonable hourly rate. Watson has 90 8-core servers and 16Tb of RAM - to rent 100 Quadruple Extra Large instances (1600 cores, but "only" ~2.3Tb of RAM) would cost you $160/hour. I'm sure there are many other differences (and the fact that you can't fire up that many cluster instances without calling Amazon first), but the idea that an open source package like Watson wouldn't be useful doesn't make sense to me.