Question Author
Thanks Curley, and no offence taken Squarebear.
It is higher than most quizzes on this site, but it is a bit more expansive than some. Also we only run two General Knowledge ones per year, the prizes on offer are a bit larger too. There are charity quizzes which cost more (eg Save the Children, Altzeimers etc). It is also cheaper than the regular monthly quizzes which aren't for charity.
As Curley says at least �5 goes directly to the charity and can be gift aided making the amount larger. The actual percentage of the remaining �2 depends on the number of entrants; the more entrants the more of the extra �2 can be donated.