Why same seller having 10 calculators new for sale at $220 people buy it for $504?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230622550020
versus
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230628177892
must be with the added rarity of having many bidders?