I've mostly heard of them being used for people doing giant international tours where they want something that just will not break. Seems like a very niche market though!

The $15k+ bikes are race bikes, which are probably never going to have internally geared hubs because they're too heavy and add too much drivetrain loss. Rohloff hubs are fairly common on high end ($5k+) bikepacking and touring bikes.

Bikes in the $15k plus range are probably targeted at professional sport cyclists, who need to adhere to UCI equipment regulations, which include the requirement for a chain-derailleur drive.

If you want to know what's premium for everyday utility cycling, look at the ebike space, where people are shelling out thousands for bicycles just to use them a vehicles. Hub gears are not dominant, but are very well represented on price points over $2k.