In the past, the only vehicles that I bought were the finished ones, Atlas, Classic Minitures, Con Cor and such. I happened into a bunch of these resin kits at a train show, and couldn't pass on the price. The guy sold me approximately 60 vehicles for $10, and 40 or so were kits, mostly Road Apples, but a couple were C in C Precision in Miniatures metal kits.
The kit that I just finished was a '40 Ford Pick-up, but there is a wide variety in this bunch, fire trucks, wreckers, box trucks, utility trucks, pick-ups, old cars, newer cars, Corvettes, Mustangs, ambulances, and a couple of Dodge Vans.
The Professor is right about the vehicles blending in to the scenery. If they aren't good enough to be front and center, why not "hide" them in an alley or a parking lot? Want more bang for your buck? Try sawing some of those ugly cars in half, and put the halves inside two different structures, the front half of a truck poking out of a loading bay, and the rear end barely visible in a garage, or maybe that "weekend warrior" drove it into a building! Got a car or truck with a missing wheel? A vehicle on a jack, and someone bending over with a tire tool almost makes me want to lend the person a hand, the urge is even greater if the person with the tire tool has on a nice dress! (not a red dress and a hairy back, doesn't work for me) How about a burned out car? Gives the fire dept, something to do, and they make that fire truck look great! Hide an abused car in the bushes, take the wheels off, (save them for details) and put it up on blocks! (just be sure to put a couple of hound dogs under the shack's porch) A salvage yard is a nice addition to a layout, perfect for those "cheap" cars, just weather the heck out of them, heat the plastic, smash them up a bit, and you turn an eyesore into a great scene.
Hope this helps out!
CJ