They pay a small administrative fee (a couple thousand dollars) to ICANN to review the case. If they win, they get the domains and transfer to their registrar where they then pay normal yearly registration fees. The previous owner gets nothing.
If you're referring to already-registered domains that Apple acquires outside of the UDRP... Yes, they pay the domain owner. If a domain isn't available to register, you can always try to buy it from the owner, and there are many places that list domains available for sale. If you are interested in a domain for development and it is parked, you should ALWAYS attempt to buy it! Yes, it may cost you a few bucks one-time but can be worth it.
It doesn't have to be that expensive. I recently paid $500 for Peepr.com which I am developing, and sold stockclub.com, which I wasn't using also for $500, both through SEDO.
(No, Peepr.com is NOT going to be porno, LOL!)
ok but lets imagine i register NOW a new domain like iphone4sporn.com... what will do apple? pay 2000$ and wait for win the case, or pay me same amount and i give them my domain immediately???