They only considered the contest cheap because doing the equivalent within the company would be expensive, take forever and possibly not produce anything usable

They only considered the contest cheap because doing the equivalent within the company would be expensive, take forever and possibly not produce anything usable. The contest, by paying out only under certain conditions, guaranteed a usable result and thousands of people working on it. So it was much cheaper than the alternative in more ways than just financially. It was a brilliant idea IMO. Releasing the data without passing on liability of some kind, maybe not so brilliant.