SpaceX Discussion Thread in Science & Spaceflight Posted May 3, 2017 Falcon 9 is now flying heavier payloads reusable than it initially did expendable. Maybe it might save a little material cost to build a shorter tank for lighter payloads, but you almost certainly wouldn't save more than half the price of a complete booster, as it appears is possible with reusability. Most of the cost is in the engines and if you cut down on mass too much you get over-engined. Redesigning that octaweb is non-trivial. Also, there are additional tooling and inventory management concerns that would eat into your savings. Finally, Falcon 9 went reuseable because Elon Musk wants to go to mars and things like supersonic retropropulsion and reusability are seen as necessary technologies. I'm convinced he'd go for this direction anyway even if it weren't totally financially optimal.