A national team has never paid up but it's a very real possibilty. The G20 of rich teams have been pushing this for a few years now.
I pay my star players millions, I 'lend' him to you and he gets hurt. Not only do I still have to pay him, but he's not on the field either. More and more clubs make a stink about letting a guy go to his national team because he ahas a boo boo.