Not sure I totally agree. I think it depends on the car, your available time, skill set and more importantly, your expectations.
If you don't have much capital but time and skills are on your side, I reckon a project is the right option.
It might be an extreme case but, Here's a link to a very rusty R100, the project is currently 15 months on and look at the results. Not to mention the money saved and it's current value.
http://japanesenostalgiccar.com/forum/forum/garages/mazda-garage/288725-saving-a-rusty-r100?_=1488281856235&_=1494883818537