I stopped buying 'valuable' items at auction after I got stung on an Omega Seamaster. After fees, servicing, I lost around £150 or so when I sold it a short while later. The sale was forced by circumstance. It wasn't purchased to flip, but I would have liked to break even.

Recently there's been a trend of buyers paying above list for items, and the auctioneers I've met are very good at performing the "you did very well, sir" lines. I think that's important to dampen the buyer's remorse.

As for the Stroud auction, my suspicion is a lot of the bidders that got carried away were basing their budgets on dealer prices on guntrader-type websites.