The study the snarky article was based on. (pdf)
The article notes that 10.1% of the overpayments are more than 10% of the amazon price, so paying 50% more must be pretty rare.
On page 3 of the article, there's a table of Overbidding and Winning Bidder's Rating. The most experienced bidders are about half as likely to overbid as the least experienced.
I have to admit, I was curious to see whether amazon gift certificates could be used as a money pump, but it looks as though the overpayments are too small to be all that useful.
First link from Geek Press.
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