Well yeah, powdered milk is often twice as expensive as fresh milk, so no wonder it's relatively obscure here. Whole milk at Costco is $6.50 for two gallons ($3.50-4/gallon at the grocery store), the same quantity of Walmart brand powdered whole milk is $12.50 (makes 8 quarts, or 2 gallons). Non-fat milk is more reasonable ($8.50 at Walmart for 2 gal), but still more expensive than liquid milk (~$5.50 at Costco for 2 gal; ~$3-3.50 at the grocery store per gal).

It makes no sense. Liquid milk needs to be kept cold in transit (we don't ultra-pasteurize), is heavy, and needs to be sold within 2 weeks or so. Surely it's cheaper to dehydrate it at the source and just ship the powdered product...

And yeah, powdered eggs is an atrocity. It's also way more expensive (like ~$0.60/egg vs ~$0.18/egg at Costco, or $0.19/egg at Walmart), and they taste so much worse, so there's really no reason to buy them either. At least in my area, I can own chickens for less cost than buying powdered eggs (but buying fresh eggs is cheaper than raising chickens). It just makes no sense.

The only reason to buy either powdered milk or powdered eggs in the US is for food storage.