It doesn't matter if, in aggregate, 50M people buy more than a manufacturer does. Each of those people will still get worse pricing than the single large-volume manufacturer would.

The economies of scale in producing the raw material will likely mean that its price will drop a bit, but the guy buying 5 tons a month will always get a much better price than the guy buying 5 lbs a month. Even if there are 50 million guys doing the same thing.

There's a little markup at the wholesaler, but if a wholesaler like Costco buys in bulk they get the same deal as a manufacturer buying in bulk.

The price each individual pays approaches that of the manufacturer, enough to make this a viable alternative. This is nothing new.