Sprint (if I remember right) pays Clearwire about 5 or 6 dollars a device and at one time, they were charging 10.
4G Wi-Max has a very small footprint so I don't know if it's worth it yet. While on Sprint I spent most of my time on 3G because it sucked so bad. While down in FL for February I was in a thick 4G coverage area and used it a lot but really only got 3Mbps down while tethering. Certainly not blazing speeds for 4G but way better than EVDO.
Hopefully, if there is any truth to any of this maybe Sprint will just tack on a 10.00 bolt on fee for the device?