"The figures clearly show that they generate 9 times in tourism what they cost to run."
Where did you get those figures?
They are simple enough to calculate by using figures from the National Office of Statistics and the British Tourist authority. HM the Queen also now runs a transparent public accounting system allowing her citizens to see what she spends in total, or specifically on dog food or Bentleys, thus:
The Civil list (monies paid directly to the royal family from central govt.) is 8M GBP per annum but when all other grants etc for building upkeep et al are included it totals 35M GBP.
The UK economy receives 11.9B GBP income from tourism annually and the tourist authority attributes some 400M GBP of that directly or indirectly to the Royals, be that visits to royal residences, spending on royal related souvenirs and a percentage apportioned directly from surveys conducted with foreign nationals as to the reason they visited england and the percentage thereof that responded that the royal family and their history in some way influenced their decision to visit Britain.
So in fact I have been a little mean as it's actually more than 9 times.