True. I've long held the view that low costs of launches basically require two things: the equipment should be cheap to manufacture and cheap to service. Shuttle violated the former big time and in all likelihood also the latter. F9 certainly satisfies the former already and there's no reason to think that it won't eventually satisfy the latter, too.
Anyway, my point is, even if all that SpaceX had to work with for reuse was the main rocket body and a pile of the majority of the engines in working order, that would easily add up to tens of millions of dollars worth of equipment, and thus tens of millions of dollars of cost savings on reflight. There's practically no way that reflight could be more expensive than a new rocket, there's just not enough complexity in the vehicle for that to realistically be possible.