... are not that punitive. Average use on WiMax via sprint was running somewhere just north of 7Gigs last I saw and the "volume" charges on that to Clearwire amount to very little relative to the overall cost of what Sprint charged for unlimited 4G plans.
I suspect that Hesse was looking at other things besides volume charges. Formost among them was that he doesn't want the aggregate of his 4G subscribers to be inclined to use more data than his wholly-owned LTE solution will be able to accomodate on sprint's skimpy spectrum bands... especially if he's unable to re-allocate the nextel bands in a timely fashion relative to his FD-LTE launch. If all of his 4g subs are data hogs, they'd more likely either have to stay with WiMax where the capacity is ample or they might move to a competitor... and there goes re-capturing the subsidy on the devices where it's applicable.
If Hesse's goal was to work side-by-side with CLWR to achieve success, he would do what it takes to grow the subscriber base and offer clear, fast, high-capacity, wide-band solutions to the oncoming rush of 4G subscribers...
... either he's unable to see that as the winning trend of the future just as it has been in 2011 (less likely) or he's so busy fighting like a child with Clearwire that he won't do the deal and kick Verizon's @zs with a superior, overall solution for the 4G market (most likely).