How much does graffiti cost?

"Millions of pounds each year"

yes, but that is quite vague, the government spends over 500 billion pounds a year.

from looking at a chart of their spending it seems only a minor amount (34bn- 5%)

- on communities and local government alone, which is where I'm guessing the money comes from to clean graffiti, so its likely that it is less then 5% of the tax you pay