Retailers don't "pass on the savings". One retailer will lower the price if they don't have to pay as high a Visa fee - to attract more customers. Other retailers will then follow suit.
Free shipping wasn't much of a thing until one retailer decided to make it one :-)
Or they will increase prices later than they would have. Which I think is most realistic scenario that will happen if cap is set. Prices don't go down, but they will go up slightly less over next few years.
Free shipping wasn't much of a thing until one retailer decided to make it one :-)