United Launch says the cost of the Delta IV Heavy is $350 million.SpaceX had said the cost of each Falcon Heavy launch starts at $90 million. But that price tag — a fraction of the cost of the next biggest rockets from competitors United Launch Alliance (ULA) and Arianespace.

David Legangneux
@dlxinorbit
Just under $400M for Delta IV Heavy, not over. The cost of the Parker Solar Probe launch is $389.1M (contract announced in 2015).

Elon Musk
That was three years ago, before ULA canceled all medium versions of Delta IV. Future missions have all Delta fixed costs piled on, so their cost is now $600M+ for missions contracted for launch after 2020. Nutty high.

Elon is talking about United Launch Alliance's plan to replace its Delta and Atlas rockets with a new, powerful booster called the Vulcan rocket. Originally planned for a launch in 2019, the Vulcan rocket's maiden launch now will probably slip into mid-2020 at least. But Musk clearly believes the test flight and Air Force certification process will delay that quite a bit longer for the Vulcan.