RE 1. - the example still stands. Travel time is best understood as falling into buckets. Roughly:

- < 1h - can go there for lunch, or as part of running some errands;

- 2-3 hours - can fly over, have a full day of work at remote location (or sight-seeing), and get back home for supper;

- 4-8 hours - can fly over, do something useful, fly back overnight or next morning;

- > 8 hours - definitely a multi-day trip.

(There are more buckets still, if you consider long-distance travel by sea or land, and then more when considering how people perceived travel in historical times.)

As long as the travel time stays in the same bucket, reducing (or increasing) it doesn't matter much to the travelers. However, going up or down a bucket is a huge qualitative change, and one people - especially the business travelers - are more than happy to pay premium for.

So back to our supersonic planes, cutting down the LA-Seattle travel time from 3 hours to 1.5 hours (and accounting for airport overhead), doesn't affect the kind of trips people take. Cutting down travel from LA to Dubai from your 15 hours to 5 hours means it suddenly makes sense for corporate executives to fly over in person for single-day meetings, where previously it wouldn't.

This is also why it's the business customers that are always the target for such ideas - regular people are much more price sensitive than corporations, and are fine with long and hard flights if it means they can afford them. Meanwhile, paying an extra $10k to get the executive on an important meeting might actually be worth it for a large company.