I agree with increasing the vowel price to $500, but I believe that this would require updating the wheel values so that there is nothing less than that amount.
It's awkward when contestants spin, guess a letter, and don't have enough money yet to buy a vowel (it's different if you have an amazing prize).
That being said, contestants don't buy enough vowels as is, and certainly increasing the price isn't going to change that.
Any tiered price system seems a bit too complicated to understand under the hot lights.
Actually, it would be a sponsor rotation between 5 companies each week:
Based on what I've seen so far this week, Wheel appears to be
losing sponsors.
Maxwell House, who already sponsors the bonus round, had a $7,500 space on the wheel. Nobody is sponsoring the Mystery spaces.
Also, the Sony card bonus for home viewers has been revoked.