The DC-X was a billion dollar research project. SpaceX first landed a Falcon 9 first stage back in 2015 and now does it every other week as a commercial operator. The idea is not new either, you’ll see rockets landing upright in 1950 cartoons.

The truth is that the “landing a rocket” part is the least interesting here, Starship is a 150t capacity reusable space vehicle that will reduce launch costs by a factor of 100x, and is to be produced en masse like airplanes.

The height is almost irrelevant, as long as Starship is at terminal velocity prior to the re-ignition sequence. It's the landing sequence of belly-flop, flip and land that has never been tried before Starship.