Well, I stand corrected.
A used car dealership or mechanic, huh?
If they don't have a website already, make life simple for them. Arrange in advance to sell them the domain with a website. It's harder to say no to if you're giving them a complete solution instead of a partial solution.
Auto mechanics don't want to think about buying a domain just to turn around and hire a web designer.
Their budget may be small. I figure you'll get an offer above $500 but should probably aim for closer to $1k to $2.5k.
If there are multiple Car Grottos, then you might add another $1k to that figure.