The drunks don't really only pay £4.50 though.
And the problem with any supersonic airliner is that it's going to be more expensive than the competition. Both for the new plane, and the fuel.
At which point you're then going to need extra types of aircraft in your fleet and that means much more expensive logistics, maintenance and training costs.
With all the latest knowledge it may be possible to make a viable supersonic passenger aircraft. It could always find a place on routes like the Atlantic (and Pacific if it can get the range).
But the airline industry is a pretty volatile one. And pretty risk-averse nowadays. I saw a comment from Warren Buffet a few years ago, that he'd calculated the global airline industry was still running at a loss. As in all the carriers combined since about 1910 have spent more money than they've taken in total revenue. And there are a lot fewer governments willing to subsidise / bail-out their flag carriers for reasons of national prestige nowadays.