That's been doing the rounds for a while. If you have visited the detailing forums, you'll find the usual threads like the guy who detailed a Veyron in the early days using similar methods and spending the hours to make the cars sparkle.
Having said that, this chap's work is per hour and you don't need to have the maximum done every time. By what the various articles quoted, £7200 for 250 hours of work. Which, I must say isn't all that great as a business, £28.8/hour plus the cost of the consumables, equipment investment ...etc, you can double that rate as a plumber. But at least the guy is proud of his work and there are many happy customers.