[Uncle Bob]

While a lot of interesting, and accurate, things have been said above, valuing a car is subjective and requires some knowledge. Knowledge comes from education, either earned incrementally over a number of years of practical experience, or compressed in a shorter time frame by paying for it. Just my opinion, and you've already beaten yourself up a bit so not piling on just agreeing with you, but I'd say you've roughly paid half for a car, half for an education with the purchase you describe. Make the most of it.