When to make a car a parts car?

All of the above. The most I have ever paid for a parts car was $700 USD.
My most expensive keeper was $1600.

It’s not that I wouldn’t spend a good chunk of change on a car, but it would have to be something very special(at least to me), complete and restorable without exceeding the end value of the car.

I gauge asking prices against values published in old cars report price guide. This brings me back to earth and to pass on overpriced turds.