I just listened to this Zev Brenner show with Dan and the panel, (
https://www.mixcloud.com/zev-brenner/talkline-with-zev-brenner-on-credit-card-scams-affecting-the-orthodox-jewish-community/)
I was thrilled to hear Dan's voice for the first time, after being a fan of his for so many years.. He talks as good as he writes! (now this compliment couldn't be any better ..)
This Zev apparently never visited DDMS, he repeatedly defines Dan's role as "Helping people with what is a good deal & what is a bad deal" and he even asks Dan to give a quick example on how to know what is a good or bad deal.. So Dan became a deal counselor for that show..
It doesn't seem that Zev did any research on this topic at all, therefor he come across very monotonous, and I'm sure Dan had the same sense, Dan has much more knowledge and expertise to share.
You also said that these merchants pay like 3% per swipe, totaling 36% per year, and of course such a business cannot sustain. I think in these cases most businesses used the cards to pay for vendors, having a free cash flow without any fees at all.