Yeah, I’ve seen this with a furniture store I bought a lot of furniture from, and they offered me a 0% interest financing. Upon inquiring for the details, it was set up through Synchrony. I’m sure the furniture store pays the bank a fee. For example, for a $5K loan, may be the store pays 10% over that loan (just a wild guess here), so the store only gets $4,500 from the bank, then the bank packags it as a 0% interest $5000 loan back to you over 3 years or something.
But there can be another upside for the bank. Depending on the fine prints on their loan to you at 0% interest, if god forbids you miss a payment to them for some reason (even if you just simply forget), they may severely punish you for it by perhaps retroactively make you pay an exorbitant interest (of 20% or more) for the whole amount minus your balance, or something like that.
I remember at the time, I opted not to do the 0% interest rate with the furniture store because I didn’t want to miss a payment by accident and be severely penalized for it. I chose to pay the whole balance with my credit card so I could get 2% back from my credit card company because I had the money to pay for the whole thing anyway.
But @WhiteHat is right, I wish the store would have offered me a discount on my purchase some other way if I chose not to do the 0% interest promo but simply pay up front instead. But maybe their deal with the bank forbids them to do that because otherwise, the bank would have been left out of the picture.