If an airplane like this meant being able to fly private, it's completely worth it. One other factor you have to consider is that this plane can probably use tiny airports which shaves a 4 hours of additional driving and security gates. I'd rather be in a slower flying plane for 7 hours than fly for 4 hours but spend 4 additional hours at security gates and car traffic.
Still, "low cost" is relative to a chartered private jet--which, emphatically, is not a service that people purchase because it's the most economical option--rather than a commercial airliner (although, if true, the SFC per passenger of the Celera would be in the same ballpark as modern commercial airliners, which is very impressive). The average domestic flight is under 1000 statute miles (https://www.bts.gov/content/average-length-haul-domestic-fre...), so this plane needs to offer compelling efficiency gains at ~500-1500 mile ranges in order to compete with existing services, unless they're strictly planning to fill the niche of one-leg, long-range flights that existing private jets don't have the legs for.
$300/hour charter price with 6 seats for a 5 hour trip (2000 miles) is about $250 per seat each way. This is pretty competitive.
(Aside: the advertised range seems like drastic overkill for something designed to offer a cheap alternative to private jets--it's difficult to overstate how much it sucks being cooped up in a tiny plane for over 11 hours, even if you have the luxury of rich leather seats, can stand up in the cabin, and don't have to pee into plastic bags. Even if a family wants to charter a private jet from LA to the Bahamas for a long weekend, it'd be miserable trying to one-leg it.)