I think the key difference is if you're designing specifically for travel on earth then supersonic jets probably are much cheaper. However, if you're designing

I think the key difference is if you're designing specifically for travel on earth then supersonic jets probably are much cheaper. However, if you're designing for space and can allocate the R&D costs to space business units, you end up potentially developing something that has better marginal costs to transport people across the earth. Basically, the R&D of building this is astronomically higher than the supersonic jet. But the (theoretical) promise is the marginal cost isn't that different. However, if you're already doing the R&D for other purposes, then you find yourself owning a system that's (potentially) better for global travel.