The main issue is that Apple FRONTED the money for the machines. That means Sharp is "borrowing" them to make stuff. Sharp is more of a "manager" and not an OWNER in this case.
Sure they'd love to BUY the machines after usenet them efficiently for two years, and they'd love to sell panels to other phone makers..at better prices than other suppliers (because they have paid off equipment) . But why would APPLE let that happen? Apple put up $500m and the machines are working for Apple full-tilt that's typically a 4-5 year commitment.
They might have financed it, but what about the expertise, set up, production process that was exclusively used to supply panels cheap to Apple? Doesn't that count for something?