On FleaBay, black walnut 2" thick is going for $6.00 per board foot. So the material he had in his garage has some value. Since it was given to him, I agree that it would be $0.00 on the spreadsheet if he is just tracking out of pocket expenses.
On the other hand, he could include the value of the walnut and I suppose the value of his work (at least at minimum wage) if he has been tracking his time to see the total investment he has made in his redesign/rebuild. I think that would be an interesting number to see.
