[Animats]

It's a response to Bezos's Blue Origins tweet. Getting to orbit takes far more energy than just getting to orbital altitude, which is the main point Musk is making.

Blue Origin isn't a serious competitor, though. United Launch Alliance (Lockheed-Martin and Boeing) is the real competitor. It's amazing that they're still using Atlas/Centaur, which, although there have been major redesigns and upgrades, first flew started in the 1950s. (Yes, the current Atlas is really a new design, using Russian engines. The Centaur upper stage hasn't changed as much; it still has the 1950s Rocketdyne engines.)

Space-X still wants the capability of landing on the barge, so they don't have to expend so much fuel to kill the horizontal vector and get back near the launch point. They may end up going with expendable boosters when lifting to geosync orbit. But they may be able to reuse ones recovered from previous low orbit missions.