What heals more per gp in 1 bite? More than half of the single-bite foods in the game, if you really wanna get technical. Cheapest heals for your money is absolutely the jug of wine, at 1 tenth of a gp per health. Sharks heal 20 hp and cost 694 gp, so they are about 34.7 gp per hitpoint restored. There is one food item that heals the same as a shark in 1 bite and is about .1 gp cheaper per hitpoint healed, the mushroom potato, but with shifting prices, that negligible difference may very soon change. As the quality of the food increases, with the exception of niche foods like the karambwan which can be eaten in 1 tick, the price per hp is inevitably going to increase. To truly judge whether your money is being well spent, you must look at the difference in price per hp compared to the increase in health restored. For items that heal more hp than the shark, the manta ray heals 22 and is about 37.2 gp per hp, and the tuna potato requires lower cooking level than the shark, healing 22 for about 37.86 gp per hp. Compared to the 34.7 gp per hp of the shark and observing the incremental shift of the gp per hp as the quality of the food increases (costing 2.9 more gp per hp to eat the shark than the preceding food item, the ugthanki kebab, which heals only 1 less; costing 2.53 less to eat than the manta ray which heals 2 more), it's fair to say that it can be considered a bit of a waste to buy sharks instead of manta rays even if you're technically getting more for your money. It really depends on how much you personally value the additional 2 hitpoints in a fight, though... but they could be the difference between life and death.

And speaking of life and death, i should also note that the tuna potato is a fantastically safe and relatively easy food item for hardcore ironmen to procure which can be acquired and prepared at a lower level than sharks or manta rays. No grinding zulrah necessary, and no need for 76+ fishing and 80+ cooking.