I look less at what a car is " worth " and more towards will I end up with a good car when the repairs are all done.

My usual MO is to pay about $ 500 for a 15 year old 100,000 to 125,000 mile non MB car / truck that needs high $ repairs ( like engine or transmission ) then proceed to rebuild engine , trans , suspension , brakes , fuel pump and so on. After all this I end up with a car that effectively has 40,000 miles and will easily go another 100,000 to 150,000 K miles. I'd rather spend $ 3,500 in parts than buy a $ 4,000 car that is going to need all of that work not too far down the road.