As a caterer and the father of 5 kids, I buy in bulk! Sams club chicken is $1.66/lb all year long for boneless skinless breasts (case price). You can find deals at the grocery store, but I do'nt have time anymore for hunting around like that. The case is usually about 35lb so it just comes down to freezer space. Between what I eat and family added in, that 35lb lasts about 10days. BTW, this is not the chicken in the freezer section, this is in the chest displays in the styrofoam maxipad containers.
As for tuna, sams is not the place. you can load up at the grocery store way cheaper.
I spend some time sundays grilling a $hit load of chicken with a good generic seasoning I make. Then put 2 or 3 breasts in a ziplock and tos in freezer. Throughout the week I can grab 1 or 2 ziplocks and use them to make lunches or dinners for the family. Easy to slice into strips for fajitas, dice into stirfry veggies, or toss back on the grill w a little bbq sauce.
...but I digress. Sams for meat and protein pwdr, grocery store for canned proteins.