Seems just a bit fishy (and unlikely) to me as well...
Now, if the item in question re-appears in a future Clean Sweep Auction, it would be cause for further suspicion/concern. Given the circumstances (and the fact that Verkman wouldn't budge off of the $800 price at the National) it would be great to hear from Steve on this matter as well.
That said, I have always had pleasant dealings with Clean Sweep, both as a bidder and consignor
Mark Steinberg