This is the underground prison economy of solitary confinement

It's common knowledge that an underground economy exists in prison where cigarettes are a common currency to exchange for commissary items, like snacks, or contraband, like porn magazines. When a prisoner is placed in a Special Housing Unit, isolated from the rest of the general population and held inside a small cell alone for all but an hour or so each day, if that, access to goods is even more difficult and restrictions around commissary products are tight. — Read the rest