Their claim is they are selling a *license* to use the thing, not the thing itself. The price is what you pay to experience the product. It's the same argument as other media (ripping music, taking your camcorder into a theater). I think it a perfectly reasonable argument.
The car example that another poster offered is not valid since the business model the car company put together bakes in the used car market.... a car has a much longer shelf life than an "experience". Another poster made the point that game makers should create a game that has a longer shelf life... sure that would be great but it's much harder and not worth the price we would have to pay for it. If you don't want to pay full-price for a game, wait until it's no longer "hot" then by it once the company drops it's prices (which is what the game companies *should* be focused on to protect themselves from reselling)