Cost is presumed to be inversly proportional to Size. If a Jumbo could be made to fly supersonic at similar costs to Concorde then it would have been a winner - except for the limited routes available. I bet it would have happened by now if the sonic boom did not exist. Would it really be that hard to accelerate 4 times the number of pax up to the same speed?

A business jet at supersonic speed is probably technically much easier to achieve but cost prohibitive.