And cloud hosting, even Amazon's, isn't always cheaper anyway. Part of what you are paying for is convenience.
It's probably cheaper when you have 1000 players, but might not be cheaper when you have 100,000. You're trading high upfront costs for, possibly, higher costs spread over a longer period of time (like the difference between buying a smartphone at it's actual cost and getting a better contract, or buying a subsidized smartphone bundled with a two year contract. You end up paying more over the long term, but at a less expensive initial cost).
[Edit:] Yeah, what hplus0603 said.