I think the Sonic Cruiser would be better built as a low supersonic airliner, say Mach 1.3 or 1.4. This gets the aircraft past the very tricky area of designing for low drag right smack in the middle of the high drag transonic region. Mach 1.3 or 1.4 is in the lowest drag area of supersonic flight, and does not require the power of Mach 2.0 flight. Drag in this speed range is close to the drag of high subsonic flight, and would have only somewhat higher operating costs. The additional costs of Mach 1.3 to 1.4 flight, while higher than subsonic flight but much lower than Mach 2.0 flight, might well be justified to the passenger for the time savings.
An airliner that could fly economically at Mach 1.3 or 1.4 would be an interesting aircraft indeed.