The prison commissary system (largely run by Keefe Group) tends to overprice and gouge for the vast majority of items they offer. This is not uncommon.
https://betweenthebars.org/posts/10910/the-prison-commissary
https://betweenthebars.org/posts/10910/the-prison-commissary
http://www.bop.gov/locations/institution/dub/DUB_CommList.pd...
http://www.bop.gov/locations/institutions/dub/DUB_CommList.p...