Older planes (like ours) are not investments like stock or whatever else. You should not look at buying a plane that needs repair and try to calculate return on investment. If this is your goal, buy stock and not a plane. We do this because we love to do it not because it might turn a profit. Besides, when it comes right down to it, owning a plane makes no financial sense.
When you all purchased your cars did you apply the same logic? The average price of a new car today is about 25k and if you’re lucky enough to have it for 10 years what is it worth? Sounds about the same price as a decent, flyable 150.
When you’re standing there looking at a project plane wondering to yourself what it "could" look like and having the means and ability to breathe life back into it creating your own unique new plane then put your calculators away and get off the phone with your financial advisor, suck it up, and get ready to write checks.
If I get 10 good years out of it like my POS car then it owes me nothing. Payment has already been made with countless hours poking holes in the sky looking down on mortal man and countless memories that I would never have had otherwise.
Oh my, I have a tear in my eye.