I think you are misunderstanding their target customer. They are not targeting people who want to buy a car, but are not sure when or which one. They seem to be intentionally targeting people who are ready to go to the dealer and buy a specific car, but hate bargaining with car salesmen.

I happen to be at that specific point right now and if their service works as described on the many testimonials on the site and one on HN, I think paying $39 for it would be a great deal.

I do think you have a point in that, folks often come down to more than one choice on a model and make their final decision based on price. I think it would make sense for them to have a plan that supports this use case.