I'm assuming there are others (like me) playing as much as possible to get to lvl 80 & 81 to purchase that previous level 85 equipment 5 levels sooner.
How about:
Make a minimum purchase of $20 and you get boosted up to the next level. If someone wanted to go from 75 to 80, they'd spend $100, or perhaps better only allow it to be used once or twice. That way the people who level'd up themselves won't complain -- although those level up bars exist so really there's nothing to complain about. Run it for 2 days or something.
Once there, they'll buy all the Nike clubs available at that level -- otherwise they wouldn't have made the initial purchase of $20 to get boosted.
So, WGT gets numerous $20 amounts as players boost themselves. Then, they get all the profits from the club purchases as well.
It's win win for WGT, as they should receive an increase in purchases that wouldn't have normally occurred b/c players wouldn't have gotten to 80 without the promotion.
It's also win win for the players who are eyeing those Nike clubs and are willing to pay for them, but wouldn't have level'd up in time.
2 win win's equals good times. :)