At least with the peloton purchase, it sounds like they are using Affirm. Generally if you have good credit, interest rate is zero. I've seen it on other high ticket items for sale online. In this case Affirm reduces the friction of buying higher priced products.
The phone I'm typing on now was financed through symphony credit. Zero interest, and 36 monthly installments. I'm sure there are penalties if I don't pay every month, but it's on auto pay.