Idk what their source was but I think you should look for cheapest “possible” to do a fair comparison (cause obviously a certain shop can have super expensive wings). Near me lowest for wings will be 3-5€/kg, canned tuna starts from 8/kg when on discount, but also has like 30% of seed or olive oil in it (so actual tuna cost to the consumer is more like 12€/kg minimum) Chicken is definitely cheaper everywhere IME.
BTW I’m talking raw chicken wings…everything pre-cooked costs more
I so wish we could get actual wheat grains at the supermarket, possibly bio. Instead whole cereals are mostly sold as animal feed (so with fewer safety standards). It’s bs. Same goes for soy beans! They give 'em out to farmers for a lot less than a 1€/kg as animal feed, but I have to order them online? While every corner shop has tofu, soy milk, etc… come on 😅