Some retail chains and restaurant has gift card sold by third parties for discount, for example, you can find a lot of GC on ebay, some are people cashing out their unused gift card and in some cases, internal theft, and some cases, other kinds of theft. Other totally legit places like Sam's Club regularly have discounted gift card with limited availability for each customer. The state of the matter is, gift cards are sold commonly around or under 80% of their face value.
Here is an idea. You get the cards at a discount, when the customer pays cash, you use the gift card to pay and keep the cash. I happened to know a gift card dealer and get them at a competitive price. PM for discussion.
I want to talk to retail people about this idea, its limitations and actual practice, and the legal and moral side of the question. Is this legal and moral in your opinion and why? I will post this in /r legaladvice
I am less certain about the legal side of things. Of course safety is the priority when doing something unorthodox. However I think when done right, it should be undetectable. This could bring in some serious cash in a busy location.