Depends on your region. Meat is never affordable from the supermarket and in-city but in areas with an active local fishing industry for an example, fish can be one of the most cost efficient sources of nutrients if you purchase them directly. Saved my life when I was going through poverty.

One should note that vegetarians exist and those tend to be (generally) more affordable due to having a bigger variety in choice while also cutting out the expensive meats. Also generally more accessible than a vegan lifestyle, is not suiting every person's metabolism. I'm now a vegetarian purely because meat is unaffordable to me currently (I moved away so no more cheap fish)