Eric Berger at Ars Technica has found that the most recent Air Force budget provides a good estimate of the price ULA charges the military for its launches.
According to the Air Force estimate, the “unit cost” of a single rocket launch in fiscal year 2020 is $422 million, and $424 million for a year later.
This is a complex number to unpack. But based upon discussions with various space policy experts, this is the maximum amount the Air Force believes it will need to pay, per launch, if United Launch Alliance is selected for all of its launch needs in 2020. ULA launches about a half-dozen payloads for the Air Force in a given year, on variants of its rockets. Therefore, the 2020 unit cost likely includes a mix of mostly Atlas V rockets (sold on the commercial market for about $100 million) and perhaps one Delta rocket launch (up to $350 million on the commercial market for a Heavy variant).
In other words, the $422 million estimate per launch is the most they will pay. Atlas 5 launches will certainly be less, about $100 to $150 million, while the Falcon 9 will likely be under $100 million. What they are doing is budgeting high so they guarantee they have the money they need to pay for the most expensive launches, usually on the Delta Heavy.
From my perspective, they are budgeting far too high, and if I was in Congress I would insist that this number be reduced significantly, especially considering this Air Force statement on page 109 of the budget document [pdf]:
The Air Force, National Reconnaissance Office (NRO), and the National Aeronautics and Space Administration (NASA) agreed to a coordinated strategy for certification of New Entrants to launch payloads in support of NSS and other USG requirements which has so far resulted in the certification of one New Entrant. The Air Force continues to actively work with potential New Entrants to reliably launch NSS requirements. The Government may award early integration contracts to ensure each potential offeror’s launch system is compatible with the intended payload. Beginning in Fiscal Year 2018, the Air Force will compete all launch service procurements for each mission where more than one certified provider can service the required reference orbit. [emphasis mine]
The “New Entrant” is of course SpaceX. They are also saying that they are going to encourage competitive bidding now on all future launch contracts.