It will make money
I don't believe the major costs of running the app store are related to the review process I would guess this takes maybe 200 staff. Adding up their salaries is a drop in the ocean for the amount spent on the app store.
I would think the major cost is hardware, as iTunes has become more popular and offered a wider variety of media they have needed more and more hardware to run it. As with most businesses they will have a continual hardware replacement programme. This I would think would lead to an increase in profitability overtime as hardware becomes more efficient.
Also since there is no reason for apple to comment on the profit it makes individually from iTunes a small profit in reality could be a lot.