When I went to the site you listed, and checked the C3, it looked like the purchase price was much more than 15k. List price was 19k, and with Meinauto discount, 17.6k.
For me it offers 15000 plus transport to the dealership for the C3, but there’s plenty of other cars for less money on the list. Also: German prices, German taxes - the pricing is likely entirely different elsewhere.
Depends on where you live, obviously, but I used to own a C3 (on the list) and it was a perfectly usable car.