I didn’t invent credit cards. I pointed out that being able to borrow isn’t the limiting factor. It’s well over 100% rate of return for the bulk savings you can get for some of the examples often cited. That’s a tad more than the interest a credit card charges (or what the charity I suggested could charge).

The point of my comment was to suggest that you be the lender and get these easy returns, if you’re so confident in the theory. Why did you think it would be relevant whether current credit cards would lend to them?