The cost of an item in a food store depends entirely on what the owner/manager(s) set it to
For example, one could buy the stock of a Burger/Pizza for around 28$, then set the actual price in store to 50$.
If you want lower food prices, then either go to a different store or get in contact with the owner and ask them to lower it
Also.. medics get missions, so can make 1200$ every 20-30 minutes if they wanted to, whereas a food store would probably make less than 200-300$ profit on that time scale (if they are lucky

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