Your logic is impeccable.
Your conclusion is totally wrong.
The "true" value of anything is what value others put on it.
Diamonds are just shiny rocks....they have value because someone is willing to pay dearly for them.
I have been a car owner/repairer/restorer for many years. Unless you own something collectable(first generation Camaro/Mustang/Mopar, etc.) You almost never get your investment back on an auto.
That is the reason you must use your impeccable logic the next time you decide to put money into an auto. The idea that I'll fix this and that and then sell the car almost always loses money. Besides, didn't you get years of service from the vehicle? Figure the yearly cost of ownwership and compare the same mileage/time to cab/bus rides. I think you'll be way ahead.
Autos are not an investment. They are transportation that wears out and needs replacing. Bite the bullet, lookup the "true" value in Bluebook, etc. and price accordingly.
You can also chalk it up to a lesson learned as you seem to have never sold a car before.
On the other hand, If you have the time, sooner or later someone will be willing to give you what you want for the car, or near it. I do mean time. I sat on a first generation Camaro for 12 years before someone finally gave me $500 less than I was asking.
These are the realities of dealing in autos.
Hope this helps-JT
Many years;many cars