In article ,
says...

That's a terrific demonstration, as proof of accomplishing what
other space agencies (including our NASA) still can not do.

Because they're constrained by politics. When Congress mandated SLS,
following the failure of Ares I and Ares V (due to Griffin's hubris) to
produce anything useful, NASA's hands were tied.

A truly reusable fly-by-rocket is a serious game changer.

Absolutely, but the reason this has not been done to date isn't due to
any fundamental breakthrough in the technology, so saying government
space agencies "can no do" this not completely true.

Wondering how much extra fuel was consumed.

Details like this will likely be kept confidential, since SpaceX is a
private company. Furthermore, reusability comes *after* stage
separation, so customers, like NASA, won't be privy to all the details
about how SpaceX is making this work. Unlike NASA (should be), SpaceX
isn't in the business of helping other companies reduce their launch
costs.

I'll be digging through on-line news reports today to find into about
the attempt to "land" the first stage of the Falcon used to launch
Dragon to ISS last week.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer