u/The_Maddest_Scorp

Watching the Space X launch and landing which is from a control technology standpoint of course quite impressive I suddenly asked myself the question from the title.

Why carry fuel up and down to save what amounts to little more than a tube of metal alloy with a computer and an engine. Isn't payload the most important criteria and wouldn't using retroburning to brake hurt double since it has to be carried up to be used? Is the tech in the rocket really that expensive to warrant this?