Suggestion:

Turn on the "subscriptions" feature of vBulletin and add a First Class membership. Set the payment to Paypal and charge $40-60 per year for this membership.

Give First Class members a separate skin without ads and some stupid "First Class member" logo on their profiles. Maybe turn on the profile pictures also. A separate First Class forum is also a possibility.

It's a great way for members to say "thank you".

/Martin
vBulletin administrator since 2001