In its basics it can be described like this:
Every buyer group has preferences regarding the 5 main stats Tameness, Sportiness, Comfort, Prestige, Safety and up to three misc stats like Practicality, Top Speed and Economy. In addition to that the buyers have a certain budget to spend up front and through running costs, which (probably) is normally distributed in that group.
Depending on the group all the main and misc stats are weighted in a certain way, with the addition of model image and brand image to get the overall desirability of a car. Then all cars on the market are scanned for which ones have the highest desirability and one of them is chosen in a random fashion, weighted by the desirability.
There are a few more things than this to the system we have in mind, of course, but this should give you a pretty good idea

Cheers!