My ALDI here in Florida has milk for $2.49/gallon.
That’s about the same for me locally - Aldi or WM.
Now I DID see cheap milk at Costco - they allowed a free walk-around to consider a membership. This was before it hit ($65 is it now?).
In Texas, the Aldi had whole milk for $1.89/gal. Even $1.69 one week when they were overstocked. But that was 5 years ago.