A US PPL is not much cheaper nowadays than a UK one. Their avgas has gone up hugely.
The chief plus of a US PPL is that you can do it as a solid project out there, in a few weeks, whereas the average time in the UK is a year due to training being constantly broken by bad weather. Of course, if somebody picked their time right and camped out next to a UK school they would do better but few UK schools are organised anywhere as well as the US ones, but few people do that because the UK option enables the training to be fitted around's one's life and income. The school I did my IR in (Arizona) was like clockwork. Maintenance and refuelling during the night, downtime = zero. Instructor availability 100%.
Some things remain far cheaper in the USA, e.g. my IR cost me something like $4k (incl motel, travel, and food etc) whereas a JAA IR is something like £15k. But that is due to other factors, not the change of scenery...
Took a Citation into Norwich for a few hours last week. The aircraft owner got a bill for about £400 to land and be handled there and thats not a major airport.
Unfortunately people like your client inadvertently create The Handling Problem
Most jet owners couldn't care less whether they get charged £400 or £2000 for having their sewage drained out and having some delicious coffee and croissants delivered by a very well dressed young lady with a very properly respectful smile and just the right amount of cleavage (the latter must be awfully hard to find within 50nm of Luton). The airport manager, being a fresh MBA from the Univ of Upper Warlingham (i.e. a clue-less moron who has never run even a chip shop) loves this kind of thing and doesn't want "dirty GA" around when these "nice customers" turn up.