Suppose you could use a balloon to get to LEO altitude. You're still not in orbit. Anything that actially is in orbit will come hurtling at you faster than a bullet. Most of the fuel used in getting to LEO is used to achieve orbital speed, not orbital altitude. So the question of ground launch vs space launch is really one of where your engines operate most efficiently, or if you can avoid air friction in the dense lower atmosphere, or that sort of thing. Baumgarnter was nowhere close to "10% of the way to the ISS."