Hmm, you get money from the state without working for it, you pay taxes to the state and the state is happy - sounds suspiciously like one of those get-rich-quick schemes, huh?
And about the tourists - ya, I´ve heard that argument before. But the UK is such a nice country, I can´t imagine a sane tourist comes here because of the current royals: they come because of monuments the royals of some centuries ago built.
And on the other hand: imagine how much productive time the British "Joe Sixpack" spends on following the royals and their scandals. If he´d work instead, the British GDP would get such a boost (it would probably be doubled