Well then take it for what it is worth. If you want to discredit the study because you think a few high-end luxury cars or median incomes vs. average incomes are skewing the data so much that it results in only one city having an income that can buy the average selling price of a car then more power to you. You can do the study yourself if you want.

Take the average OKC family income and calulate what 10% of their gross income is.
Divide that by 12 to determine what they can afford for a monthly payment
Go to a loan caluclator and see how much you can borrow at that monthly rate for 4 years (and you can pick the interest rate).
Then find out what kind of car cost that much.