[jfk13]

Interestingly, I just noticed a Zip Pay option here on a UK retailer's site, and in this case there doesn't appear to be any flat fee involved; the 4 payments add up to exactly the standard retail price of the product. I guess this probably varies depending on local credit-issuing regulations.

(Checking the T&Cs shows that they do have a steep fee for any missed/late payments, in addition to whatever cut they're taking from the merchant. But it looks like here, the few weeks of credit really would be "free" to the customer provided payments are made on time. Not that I'd consider using them; my cashflow isn't so constrained that I need the service -- and if it was, I'd be more concerned about the risk of being late with a payment and getting stung for extra fees.)