At the beginning of the episode, Dahmer receives a fan letter which has a five dollar bill in it. Inmates are not allowed to have cash. The money would have needed to be sent to a different location to be put on his "books" so he could spend it at the prison commissary.
Dahmer receives several pieces of fan mail that have cash enclosed. Inmates are not allowed to have cash. The money would have needed to be sent to a different location to be put on his "books" so he could spend it at the prison commissary.