Due to the increased volume of US overflights that don't originate or land at a US airport, the FAA is increasing the rates.
Per Aviation Week:
New FAA Overflight Charges Could Be Contentious
The FAA is proposing a hefty rate hike on the fees that it charges operators of flights that transit U.S.-controlled airspace but do not takeoff from land in the U.S. The action is causing friction with a rulemaking committee that requested a lesser increase. Operators of so-called "overflights" today are charged $56.86 for each 100 nm flown in en route airspace, and $21.63 per 100 nm in oceanic airspace, in accordance with rates the FAA set in 2011.
Per the Federal Register:
https://www.federalregister.gov/articles/2015/08/28/2015-21293/update-of-overflight-fee-rates (https://www.federalregister.gov/articles/2015/08/28/2015-21293/update-of-overflight-fee-rates)
Table 1—Proposed Rate Increases for Enroute and Oceanic Overflights.
Rates are per 100Nm.
Enroute rate Oceanic rate
Current Rate $56.86 $21.63
October 1, 2015 58.45 23.15
October 1, 2016 60.07 24.77
October 1, 2017 61.75 26.51