All work is value-based. Never forget that.
No clients care if you spent 80 hours a week not solving their problem, so why would they care if you spent 20 solving it?
This has not been my experience at all. It's a different subject entirely, but it is very common for clients to be much happier to pay for 20 days at $550 a day than 5 days at $2,200 a day, even if they got it two weeks earlier. People are not rational.
It's complicated and pardon me if I have glossed over the details somewhat.
If you're smart, you get all of the work done in advance, then stage it over the course the next few days, providing a steady trickle to create the perception of steady progress and to have something to mention at the standup meetings. I suspect a good percentage of experienced developers with good customer management skills do something akin to this.