Compare fresh, frozen and canned fish cost per serving.
Fish forms have wildly different edible yields, so shelf price per kilogram is close to meaningless as a comparison. A whole round fish yields roughly 45 percent edible flesh once the head, frame, skin and guts are gone. A fresh fillet yields around 82 percent after cooking loss. Frozen fillets carry an ice glaze that is real weight you paid for but will never eat, dropping them to about 72 percent. Canned fish, priced on drained weight, is essentially all edible. Once corrected, whole fish at half the fillet price often works out dearer per plate.
Edible weight
Edible g = pack g x yield factor
Cost per edible kg
Cost = pack price / edible g x 1000
Frozen fillets are coated in a thin ice layer that prevents freezer burn. It is legitimate but it is water you paid fish prices for, typically 5 to 20 percent of the pack weight. Labels that state a net weight excluding glaze are worth seeking out for accurate comparison.
Sometimes, if you use the frame. At 45 percent yield the flesh must be under half the fillet price just to break even, but the bones make excellent stock and the price per kilogram is often a third of fillet. If you will not make stock, filleted is usually the better buy.