I bulk buy flakes as well, though I use it less and less. When I had a lot of livebearers, I had to. They eat like teenaged boys.
Now I culture a lot of food and only have a few 'flake tanks'. I am trying to buy locally to support stores, although the price difference hurts. I just paid as much for 250 grams as I would for twice that in bulk.
I quite like to use the soldier fly larvae based bug bite foods, and I can't get those is reasonable bulk either. I have to admit, I have never had a bit of brand loyalty, other than the fact tetra min flakes smell like when I was a child. I don't buy them for that! I don't snort fish food to feel young.
Ingredient loyalty is different. And it's essential to have local stores, so since I don't get my fish through them, I try to support them as much as I can via dry goods. But there are limits.