New car

Here's my thinking. If i buy a new car say every 2-3 years would this be better then keeping a car 10 years ? Some math.
My car worth 6k. I buy a new car for 20k finance it and payment is about 250 month. Now if I can do that for 10 years and keep the payment at 250 a month which is 3k a year for 10 years is 30k.
Now I paid 22k for my car and it's paid off and 5 years old. I figure I will need about 1k a year in work or tires etc. So in a 10 year period I would spent about 30k. With a new car u most likely won't need repairs or tires getting rid of it every 2 to 3 years. So over all cost is about the same after 10 years.
Am I missing anything ??