$20?
Porsche add-on pack with at least 10 cars, from Carrera GT to 997/998 to Cayman R to Cayenne. Obviously all premium but they should also do some older models, too.
Otherwise, I would want big bundles of cars. If it wasn't going to be all make packs, I could see something like:
American Domestic Market pack with Cadillac CTS-V '04 and '11, Escalade '02 and '07, Escalade EXT '07, XLR-V '04, 1966 Mustang GT, 2000 Rustang GT, 2000 Lincoln Navigator, Honda 99-00 Civic Si, 2006-'10 Civic Si, Acura '99 Zanardi NSX (no reason we can't have that right now, since they just paint the roof of the 91 and put different rims on and mesh engine cover), Acura NSX Premium '04 (mostly same as Zanardi, it's just a damned emblem and flip the steering wheel to the other side with only slight change from the premium 2002 NSX-R model )
If they were all premiums I would pay $20 for that.