There's a huge variation, here, at most every store between the primary dairy brand and the store brand.
I usually buy 2%.....at Walmart, it's $4.98 for the dairy, and $2.58 for the store brand. I was at the neighborhood grocery the other day, picking some up and the dairy brand was $4 something almost to $5 and the store brand was in the low $3 range.
Occasionally the Pilot runs a special on the dairy brand...but unless we run out, we don't get it there...because it's just a block over to the neighborhood grocery.
I don't drink milk, but the Boys go through a gallon about every 2 days...and both have said they can't tell the difference between the dairy brand and the store brands.
I used to only buy the dairy brand for sour cream, whipping cream, cottage cheese, ice cream and french onion dip. They don't make butter for some reason. The only thing I still consistently buy is the french onion dip....no one else's is any where near as good. Everything else is just too expensive for very little taste difference.