Yes, there are unquestionably premium pax who will pay for J (biz class). Airlines love these pax. But the same fuel cost dynamics apply to J as they do to Y (economy). So any J seat in a supersonic will need to have exponentially higher pricing due to exponentially higher costs (which is why Concorde fares on BA were much higher than F fares on subsonic aircraft).

Since Concorde cost the airline nothing to buy (the plane was given to the airline for free), BA was able to make Concorde operationally profitable for a while based on the amount of demand for ultra-premium service on the London-NYC route and some charter business. But the singular nature of the NYC-London market (the province of exclusive bankers, lawyers, and media stars) makes that route unique in the world. AF never really made money flying the Concorde on its regular Paris-NY service.

And not long after the AF crash, the Concordes in operation were facing upcoming D Checks due to the total n of hours in service. A regulatory-mandated D check involves a total dismantling of the airplane for inspections of the airframe. Given the enormous cost of a D check, in most instances airplanes reach the end of their operational life at that point. No way did it make financial sense to do this. Concorde’s days were effectively over.