I am a fairly hard-faced cynic but I've paid ££ for it twice and absolutely loved it. Will def be going again.
For me it's largely the 'magic' for DS (he was 3 on his first trip, just on the cusp of not really 'believing' in the characters but also sort of believing because he wanted to), and also the enforced fantasy of it all. I'm a single parent, I have a demanding job, too much housework, an endless list of boring shit which needs to be done, various worries about the way the world is headed, and I will gladly pay £££ to be flung into an absurd world where all of that feels so far away for a few days. I wonder whether some of that also applies to some of the adult fans who don't have children and get really into the whole Disney thing? I've had some other brilliant, adventurous, restorative holidays with DS, and DLP was also knackering in its own way, but there was something about how immersive it was which prompted an almost addicted response in me - I started planning our second trip almost as soon as we'd got back from our first.
Probably that need for distraction could have been met in other ways, and probably the 'best' thing to do with the same amount of time and money is to spend it actually addressing the humdrum stuff rather than running away to Disney, but it did me good and there are worse ways of getting that feeling.
Re: the customer service - I know lots of people rate US Disney miles ahead of DLP for this reason (I haven't been - not a keen flier) - but I'm much more comfortable with French customer service than American! I think actual rudeness is rare, it's just a more reserved culture and I get a bit awkward with people trying to jolly me up too much and shop assistants talking to me as if I'm a good friend, so it suits me better! I think DS is the same.
It's a rip-off for what it is (and keeping an eye on prices, seems to become more and more so all the time), but we'll definitely be going again once DC2 is a better age for it.