There's a great article about prison radios and MP3 players, and a particular model of Sony FM receiver that is like 30 years old but incredibly popular in prisons due to battery life or something... Gotta track that down.
Devices need to be approved for prison use. 3G but no autoupgrades, or appstore but no external communication, sometimes the cover must be transparent. Probably no competition in that sector, therefore they can charge whatever they decide.
Hence it's not "cheap e-book reader, top of the range tablet", but "expensive e-book device, bottom of the range reader", if you follow me.
