Yeah, this is the critical part. We still don't know what kind of reliability to expect from the used stages, and we don't know how much it's going to cost.
Right now it is, but as they built the rocket, they are able to repair it and save money for sure. From what Elon said, landing was the tougher part. He was much more sure about being able to relaunch some of the stage 1s (except 1) than about being able to land (which took a lot of effort)