I can't talk about the US but over here (Austria) the slow chip readers typically are GRPS based and connect for every single transaction. There is one nearby in a lunch place where I really consider telling them how to hook it up with their wifi :)
I recently helped a shop connect their terminal to the wired connection instead of the POTS one. The time it takes for a payment to go through went from 25 seconds to 2 seconds :)
Also they used to pay a few cents for each transaction...
