Had to buy milk today so I checked the coolers. My Safeway has 7 coolers devoted to milk of various kinds (whole, reduced fat, organic, soy, etc. etc.). Of the 7, 2 were organic, a proportion which surprised me a bit. The Safeway doesn't serve the richest clientele in the richest county in the country; lots of immigrants live in the area, though many of those are doing well. But 30 percent organic is pretty good market penetration.
And, although the taste tests in this Grist post were a bit inconclusive, supermarket organic milk came out pretty well.