[All Darc]

Redpoint, remamber that stores (or some brands with health philosophy agenda) and marketing put the prices as much high as they can fool consumers. A extract from rice, the little thin skin of rice, it's a very rich nutrient, but is removed for make white rice, instead of wholegrain rice. On Europe this residue it's sold by high prices as nutritional suplement, but on Brazil they took tons of it to feed cows.
Brow sugar it's cheaper to produce than white sugar, but it's sold by higher prices to final consumers than white sugar.

Prison can buy from wholesallers or even producers of soy protein. You can't judge prices from the small store in the corner of the block or from a brand that put photos hot female models making gym.

About expired food. It must be checked to see if it's not good for human consume, since the expired date it's a estimation and not a very precise thing. It it's stil usefull it can be used, if it will bew consumed fast. In prison I think the high number of people make stocks last short time. But without checking quality, and especially it expired by a considerable time, it's cleary a crime.