The question isn't whether they could reduce operating costs per launch vs. SpaceX. It's whether they could reduce them by enough to pay back the R&D costs, and the cost of building a much more complicated spacecraft than SpaceX's current line of boosters. (I wouldn't say that about SpaceX's planned ITS -- but that has capabilities that _Skylon_ can't touch; Skylon itself, last I checked, was never getting out of low Earth orbit, so even GTO comsats required a second stage mated to the payload in the cargo bay, a la the old Shuttle-Centaur plans.)