Having the plane in the air for less time can lead to lesser costs also: you don’t need to pay your pilots or flight attendants for as many hours, and can fit more flights in using the same plane per week. If the fuel cost and maintenance costs aren’t too much higher, it could be a big win beyond just getting passengers to where they are going faster (like track and carriage utilization for HSR).

I'm pretty sure flight time is not the dominant labor cost. It's docking and going in and out of the airport and pre/post-flight prep.

Flight crew is paid for time in the air (well, while the door is closed).

But even then for a long haul, that stuff isn’t as significant. Conversely, for a puddle jumper with quick turn around, not as much either.

Pilots are generally only paid for actual flight time. At scheduled airlines, dispatchers do most of the pre-flight prep.

They predict that there is demand for the service at a price that would make operation profitable.