Vegas is the perfect place for ladies to charge more. I think the whole marketing campaign around "what happens in Vegas, stays in Vegas," really applies, it is the place where many from middle America can let their little inner demon out, so to speak. I would think there are a lot of more casual hobbyists or curious hobbyists who go for it in Vegas simply because they are in Vegas.
For example, there are lots of other convention cities, but I think your buttoned up professional is more likely to take the plunge in the whole Vegas environment. Crap, all you have to do is walk through the casino at any of the hotels and you will see beautiful ladies in very revealing outfits and it just screams "come on boy, do something you would not do at home." Then there is the fact that you have people who go to Vegas to gamble, see the shows, shop and they are already spending a ton of money, spending another $600 bucks per hour here or there is simply part of the whole package, no biggie. It is not so much that they are Howard Hughes types, Vegas is simply a place where a person is more likely to indulge and give themselves a proverbial "treat" of one kind or another. And of course, then add to that that many people who do frequent Vegas do have a ton of money and it really does make it the perfect environment for the prices to be higher than in other cities.
While it is very competitive, there are a lot of guys going through that city, if I were an attractive provider, I would probably be in Vegas, it is simply smart. Of course, during the inevitable downturn, it is probably also a place where the ladies really hurt, precisely because it is competitive. If you have found great ladies in the $200 range, it is probably a well kept secret, but there are many high quality ladies who charge more along the $300 to $450 per hour that the rest of us are used to paying in the rest of the U.S.