"With an advanced rocket you can do maybe two to three percent of your lift-off mass to orbit, typically. And then reusability subtracts two to three percent. So then you've got nothing toward or negative and that's also not helpful. So, the trick is to try to shift that from two to three percent in the expendable configuration, to make the rocket mass efficiency, engines efficiency, and so forth so much better so that it moves to around three and half to four percent in the expendable configuration and then try to get clever about the reusablility elements and try to drop that to around the the one and a half to two percent level so that you have a net payload of about two percent."

http://youtu.be/vDwzmJpI4io?t=27m

(Watch from 27m for about 50 seconds.)