V.M.
I find half gallons of house brand organic milk for $3.69 and whole gallons at $5.99 at both Whole Foods and Trader Joe's, and the quality is consistently good. They're also not ultra-high-temperature (UHT) pasteurized, which can give you a cooked-milk flavor. The Kirkland organic milk at Costco is UHT in the 1.5 gallon box packs.
I find the UHT milk in shelf-stable Tetrapaks to be useful to keep on hand in case of milk/snow emergencies, and I've found that at Whole Foods. Treasure Island has nonorganic milk tetrapaks, and there are, of course, the wildly expensive juice-box sized milk tetrapaks, too.