I can think of a few ways (not sure all within TOS), not sure if helpful but still worth a shot (maybe):
Build a site for people wanting to buy a car and know what's the avg asking price of models with the same characteristics.
For example: say I want to buy a Freelander for max 10K. I'll go and check all freelanders and quickly notice that most in that range are from the year 2010 and 2012. Kilometers differ, guarantees, etc.
For me at least, I go into each and mentally account what's important and compare to decide which ones I'll contact.
I could use a service that would weigh all the variables and basically say to me: these 3 offer the best value for the money and within your price range.
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If you are able to build email lists, I'll just leave this here: you can upload Look A Like Audiences to facebook to advertise to similar people as your email list.
I'm sure you can see the possibilities here. Sorry I don't go into details as I'm mobile.