It's been a year or so since I did it, but when I used a Coinstar machine, there was no fee if you took your payment in the form of an Amazon gift card (there were several other retailers too, like Home Depot). In other words, if you turned in $30 of change, you'd get exactly $30 to redeem with the vendor. I assume the vendors are paying Coinstar something on the back end for driving the business to them.