This ^^^^ is a VERY good point. Thank you!
Couple random thoughts ...
I never really minded paying the buyers premium. I know there's a cost involved with the venue (plus all associated expenses), advertising, insurance, etc. And there is certainly a value-add to bringing lots of cars together with lots of buyers (by the way, if 10~12% buyers premium sounds excessive ... try buying a COIN at Heritage Auctions, where the buyers premium is now 22%)
Where I have a problem, is not knowing if you're bidding against real buyers with honest bids. Are you buying in a competitive, or manipulated, market?
Anyway, as far as i'm concerned, this thread is un-hijackable. Please feel free to add as many stories you like about deals gone wrong! My only request: offer a take-away, or lesson-learned, that might be useful to others in the future