You raise the market value of pistachios when you peel them

Your logic isn't cracked, but unfortunately it does nut work that way in practice. I blame shell corporations.

The same goes for cooking, making coffee and a LOT of other things you do at home. It raises the market value because it's a chore some people want others to do for them.

If I buy a bag of pistachios can I shell them and sell them back at a higher price?

Literally manual, nice

I think of it as sweat equity.😉