I added up all the receipts on my first full restoration project back in the late 80s and found when I sold it, that I made $17.85 which came to about 2 cents per hour for my time. That was while I was in college, working a full-time job for part-time wages, i.e. a relative budget build with even a home garage paint job. Now I'd more typically spend $9,000 on a paint job and very few cars are worth enough to "justify" that kind of restoration expense. I still always keep the receipts for each project, but only just in case they are needed to exchange a defective part, invoke a warranty or if a buyer wants to review them. I would NEVER dream of adding them up. I don't want to know.