I don't think he stands a chance, except if he finds an idiot. I've seen C5s in top condition NOT selling at €350, but going at second round for €300. The average price for a one in good condition is between €300 and €400. The top price I've seen was approx €600 with all the accessories you can think of.
Being the killjoy that I am, I sent him the article no of the boxed C5.