Cost benefit of non dom

There was a certain amount of fuss in the papers over the weekend over the non dom tax rules which allow rich individuals to spend a lot of time in London without being domiciled here for tax purposes and hence avoid paying a material fraction of their earnings in tax. Now whether you think this is fair or not (and I don't, but that's an opinion) the real question is whether the amount of wealth created by letting these guys live here without paying tax is worth the lost revenue. I'd love to see a proper cost/benefit analysis here. Wouldn't that be the best way of deciding whether non dom makes sense and, if not, how to change it? What policy would maximise the total benefit to the UK?