But have a look at this:
http://annonces.ebay.fr/viewad/RARE-Saxophone-COUESNON-Monopole-Conservatoire-La-Grave/5043496437
Both amg's link and my link are of a sax in Strasbourg
The Ebay auction in the OP is currently at less than 1000 euros.
The Ebay action above seems to have a price of 2500 euros.
Looking at the pictures, they are of very different quality, but they look like the same sax and case. Comparing the cases, there is a circular mark in the material just up from the left handle post, and identical white areas near both hinges.
The saxes look identical, with the same plate wear on the bell pictures and engravings look identical, and scuff marks on each instrument.
So is there something about French Ebay I don't know? Are these 2 auctions of the same horn, or a legit way Ebay.fr works with a buy it now price as well as an auction (but why different photos) or are my eyes seeing things that are not actually there?