Happens all over within the US. There are massive underground economies of this stuff. Folks on the draw buy stuff with their EBT and SNAP bennies. Sometimes they sell it right back to the very same store they bought it from, at a discount.
Welcome to the concept of 'fungability'. EBT dollars are almost as fungible as cash, since you can readily transform them into cash via methods like this. Indeed, this is part of why just giving welfare recipiants cash is normally as good as giving them restricted goods - because if they want/need cash more than what you're giving them, they'll sell it for money, one way or another.
Ever consider that maybe the reason they're doing what they're doing is less because they're abusing the system than because the system isn't flexible enough to meet their REAL needs?
On that note I'll say that I support 'workfare' over 'welfare' in most cases. They'll get unrestricted money in exchange for their work, but at least they'll have to work for it.