Neat.
Very neat!
I do agree, it can benefit from at least a couple more cost items. You've already mentioned one; repair/maintenance costs. Another that should perhaps play into your equation: "Opportunity cost," -- the cost of having your money tied up in an (object) rather than in an investment.
Given your initial state -- "having to buy a car" -- the minimum cost of any (acceptable) vehicle isn't the issue here... but the cost differential between the lowest priced possibility and the others might offset some other factor(s) -- differential milage, repairs or insurance, just for example.
:-) But, before you get too rational about this, remember what a wise economist once told me: "Rational considerations aren't the whole issue, when buying a car."
