Well, I don't make my living off of growing grapes. I just do that part for fun. So my napkin math is basically $1.50 per pound, which is on the low end of what I pay when I buy them from a vineyard.

Real grape growers are looking to maximize dollar per acre. There's a lot that goes into it if you're trying to turn a profit. But at the end of the day it's about keeping the yield high and the input costs (especially labor) low.