Current aircraft are significantly slower vs 50 years ago due to fuel economy issues. At 30,000 feet airlines could fly just under 678 mph, but they actually ~575 mph. This pushes up the benefit of supersonic flight.

On top of that the top 0.1% is both larger and more wealthy making filling ~50 seats a flight at 30,000+$ a pop easier than you might think. Drop that into $5,000 territory and some people would this every week.

IMO it's actually business jets that are the best market. They fly fewer trips making fuel less of an issue.