Dale
That is the thing with REAL no reserve auctions (not pretend ones). You will see results much higher than seems reasonable, and results much lower, simply because those selling prices truly were set by two real bidders.
I have been hearing the "if only I had known some prices would have gone so low, I would have bid" refrain lately, and the only answer to that is to either make every effort to be at your computer when the auctions are closing, or to put in a bunch of "joke" low bids and know you will only get a few of them at best.
As to why some things go two or three times what you think is fair and others go half or a third of what you think is fair, it is because in most cases the bidders have FAR less knowledge of values than you do, and sometimes they have no clue at all, and if they run into another REAL bidder in the same boat, the prices sometimes are silly.
The beauty of this is that you can get real steals, but if that consignor got a couple of the high prices as well, he is likely to still be real happy with his results overall.
Bruce