Maybe someone else has some more info than I, but I have a Dior saddle bag that is very similar to those picture, but is smaller and it was $250 about a year - year and a half ago. I saw bags @ Dior in Boston this past summer similar to the Dior bags that are pictured and they were quite a bit more expensive. I don't have any experience with that site, but I am weary --I don't have any proof though.
Hopefully someone else can help more than I can.