And to further elaborate upon George's response:
The amount that was required for the purchase is what matters.
While it certainly matters to the buyer and the seller in that particular transaction, it matters much less to anyone interested in knowing what another example could be bought for, or sold for. In this regard, what the high bidder was willing to pay is entirely relevant.
So if one of these should show up on a pen website for sale at $1000 or more, we know the only reason to pay that amount is because you absolutely have to have one, even though you'll be overpaying relative to attaining one at auction.
Again, just because one sold on eBay at $500 doesn't mean you'll be able to buy the next one there for $500, or anywhere close to that, even with the same bidders participating.
Nor am I speaking just as a dealer. As a collector, I've bought items that I knew were bought on eBay for a small fraction of what I willingly paid. I knew they had slipped through and were bought for way under the money, and that my chances of getting another example under just those circumstances and without the winning bidder participating were vanishingly small.
Edited by David Nishimura, 10 November 2012 - 11:10 PM.