canned tuna in the us is pretty cheap, though there is varying qualities (basically how many guatemalan children's fingers you want ground in with the meat, some or none). Canned fish can be had for anywhere from .50-1$ a can depending on the size of the can. Good albacore tuna costs like 2-3$ a can/bag. Frozen tuna is pretty pricy at around 7-10$ a pound iirc. Frozen chicken is like 2-3$ a pound. Basically it's the same here as there, buying frozen and in bulk is the cheapest (if you're dollar cost averaging) but for the OP's purpose canned goods are just fine.