If supersonic flight is so expensive that less than 1% of the population can enjoy it its not clear why the rest of us ought to tolerate it
Eventually, that means that there will be some seats in the back of the regular plans for everyday wage slaves.
It's not more viable now wealth inequality just means that there are more rich people to benefit.
You could have used the exact same argument for normal flight 100 years ago. Supersonic flight being more expensive than normal flight doesn't mean it will always be too expensive for the masses unless you assume there'll be no more economic growth ever.
The low-volume, high-priced rich-person toys (Roadster) finance the scaling up that enables lower-priced mass-manufactured product (Model 3).