I’m trying to estimate what could be the lower limit of how cheaply a spaceplane could ever put cargo into orbit, assuming a spaceplane could be built and operated for a reasonable price. In other words, suppose the spaceplane itself was no more expensive to build and operate than a commercial airliner, and the only real problem was the low payload ratio needed to achieve earth orbit.
For purposes of comparison, I’m thinking along the lines of what airfreight on a 747 cargo carrier costs. Assuming that only 3% of the gross takeoff weight of the plane was payload and the rest of the capacity had to be devoted to fuel, what freight cost would that work out to?