Market overview: Which Fiat models are currently the most popular on the used car market? AutoUncle has analysed 5,619 used Fiat cars that are currently for sale at 46 dealerships. The three most popular Fiat models as used cars are: 500, 500e, 500C. Prices start at around £2,499, and the average price for a Fiat on today’s used car market is £7,572.