The problem is that they made the bed, and now they have to lie in it. There's no good way to break the news of "yeah, due to these trying economic times, we've had to totally revamp the vowel buying system so they're a lot more expensive" without coming off looking like complete arseholes.
That said, of the ideas mentioned, I think I like the idea of escalating prices the most, 'cuz it lets you *kind of* mask the bad news. Start 'em at $250, double the cost of each subsequent one, up to $4k for the fifth one. You'd put a "NEXT VOWEL" reminder on-screen, much like they use in the Jackpot round now.
But no matter what you do, it's going to be a hard enough sell that in terms of viewer goodwill it's just going to be less of a hit to let it go and the 12 people in the viewing audience who are bothered by it will just have to live with it or take their eyeballs elsewhere. And with all due respect, the sort of person who would be indignant enough to stop watching over something like that is also the obsessed sort who will NEVER STOP WATCHING FOR ANYTHING. So Sony's pretty safe, on the whole.