And, of course, they don't just "bear the cost of an idle server". Just like any other fixed costs in any other industry, those costs get smeared over the charged prices. Unless there is some serious economy of scale (i.e. ops at Amazon managing to handle the upkeep of a 1000 of their servers for less than 1/1000 it costs you to manage 1 of your server), you're ending up paying somewhat more. But then again, you don't have to spend time to manage your own server which is probably a positive trade-off.