Man, they been promising parabolic trajectories since the Asimov days. Regardless of the cost of the airframe, how cheaply can you boost a full cargo of meatbags into very low orbit and then stop them again on the ground? And I'm not getting on any vehicle that has to glide into a landing, getting exactly one chance to get it right.

Fuel. Fuel is the answer. Figure out how to make it cheaply enough and you have a chance.