You're assuming the buyer was planning to fully restore the game and resell it for a profit. Maybe he/she just wanted a MB that was less expensive than the fully restored examples on eBay/MrPinball and didn't care about the cabinet decals or whether there was some wear around the scoop or Drac-track.

Please correct me if I'm wrong, but isn't it 7% sales tax plus 10% buyer's fee *if* you didn't bring anything of your own to sell at the auction? If the buyer was a home user but *did* bring something from his/her own collection to sell, the total would have been $6100. They might have preferred that to paying $8500+ for a fully restored MB if they just wanted a machine to play.