It'd be interesting but I'd think it would be a bit tricky. Used vehicles can vary in quality greatly from one to the next, depending on several factors - the climate they were driven in (are they rusted out?), the type of commute the owner had (did they drive on city roads? Highway? Country roads?), and how roughly the vehicles were driven (I know people who drive like they think they're racecar drivers and it's hard on the engine/transmission). Supply and demand also differs greatly - some people live in areas where trucks really hold their value, or all-wheel drive is seen as worth paying a premium for, or where gas-sipping cars are popular, etc., and this can affect the price of used cars in their area. Two vehicles could be the same make, model, and year, and be selling for the same price, and one could be a huge rip-off while the other could be a great savings, depending on the condition of the vehicle, maintenance records, mileage, part of the country, whether sales tax has to be paid on a used car, etc.