Tuna potatoes heal up to 2125 life points each, making them one of the highest-healing foods in the game. They are a fairly alternative food compared to fish, but they are still in high demand due to their relatively low price. Before buying lots of ingredients, test out the profit by making one tuna potato. Both potato with butter and tuna and corn have a buying limit of 1,000 per four hours, so only 20-30 minutes of supplies can be bought at once. It is useful to leave in an offer overnight for the ingredients so you can make more at once.