low-bandwidth data plans in bulk are pretty cheap. it's what many atms, vending machines, redbox and similar, etc., along with sensors and gauges, and what-not for a variety of applications, use.
over the expected lifespan of a car, it would cost the manufactures less than they charge for a set of floor mats.
even netscape/mozilla was in on this game, with the open directory project (dmoz). aol eventually shut it down, but it apparently lives on independently as curlie.org - but i have no idea how current it is or anything.