I'm pretty sure this person has not in fact seen people selling milk they get from EBT. Unless you get industrial amounts of milk from EBT, how would you even go about selling whatever amount you get? I'm certainly not gonna buy a single carton of milk from a stranger in a parking lot. To get any buyers at all they would have to sell at well below market price, which is a real problem when you're not dealing in valuable commodities like drugs, but trying to sell a very limited amount of milk. Combined with the amount of work you would have to put in to hawk single servings of milk to strangers without receipts or any quality control I just do not see this as a viable business idea even as supplementary income and I did not even have to leave the liberal mindset to arrive at that conclusion.

What this person might have seen is someone offering a glass of milk to friends and family who are also helping them out economically. That makes perfect sense and is a nice thing to do, but isn't really a question of selling milk.

Or maybe EBT delivers industrial amounts of milk. If the tonnage of milk you receive is large enough it would only make sense to try to sell it.