Interesting fact! (to those who think the royal family are expensive) the royals cost us 61p per tax payer per year. So I'm fine with it, given the tourism revenue etc.
That number is old and the cost figure in 2009 was actually £41.5million. It seems to go up every year. However, the number is still the highest expenditure for any of the inbred royal families within Europe. It was 6x higher than the inbred Spanish royal family.
In addition, the number is actually only a small fraction of the actual expenditures as it excludes security costs, military involvement in royal events, and other properties. Security costs alone are in the hundreds of millions.
Also, I would argue that they cause a decline in tourism revenue than if they were removed. Entire palaces, art collections, etc. would be open to the public.