For me, I am all about cost of ownership.
For every $1,000 I spend on the cost of a vehicle, I expect to get 1 year of use, and 10,000 miles. I also expect all cars to be worthless after 130,000, so my 10,000 miles per thousand can not go beyond that threshold. All other miles are gravy, and "free miles".
I will not add to that the regular cost of maintenance. If a major repair is needed, I will first ask myself if I expect to get another 10,000 miles and 1 year of service for every $1,000 I am about to spend.
If a new car costs $24,000, I would require 24 years of trouble free driving, and over 240,000 miles with no major breakdowns. Not likely(and in fact impossible with my 130,000 mileage limit), so those cars are not an option for me.
I do not always meet my target. My worst vehicle has cost me $1,400 per year of use.
My latest:
A 2008 Honda Fit with 73,000 miles for $5,500, bought summer 2018. I am hopeful this will be one of my best vehicles ever.
A 2000 Ford Ranger with 74,000 miles for $1,800, bought 2 days ago. This one is admittedly a gamble. It test drove so well, but is by far the oldest vehicle I ever purchased. I am asking a lot to get another 2 years out of it. My 2002 Ranger blew an engine this summer(only 94,000, bummer). A replacement would have been a used engine with 144,000 miles for $2700 installed. It would never have passed my requirements, so time to say goodbye(this was my $1,400 per year vehicle).
I recommend everyone use a similar comparison in an effort to normalize different cars to see if they were "worth it" for you. If $1,000 is too low for you, just choose an amount you are comfortable with.