I wish DS1's trip was £8. The trip itself is going to cost me £11.60 (?!) and then they say that the DC will need £5 spending money. And no hint of fucking 'voluntary' on this form - just a 'gentle' menacing reminder that as this is a 1-form entry, if EVERY DC in the class doesn't pay, then the trip will not go ahead as they will not be able to cover the coach costs.
The reason for this is because the first year this 1-form entry was at school, the school didn't run a trip. The majority of the parents who are rolling in it and can afford it found out that it was because the coaches seat 65, and the school couldn't cover the coach hire on the 'normal' charges for 30. So these mums told the school that they didn't care if they had to pay double as long as little Johnny got his school trip. So the three parents in the class that are either on benefits or very very low incomes have had to pay double for every trip, and the letter threatens that if we DON'T pay, then no-one in the class can go.
Fuckers. And because the majority of the parents can pay double and are happy to do so, we get lumbered with skinting ourselves even more to do so.
And we can't send less than the requested spending money, as they get picked on by other DC telling them that their parents don't care about them enough to give them spending money. 
I have this in DS2's year too, but because it is a 3-form entry, thus requiring 2 coaches. And as the precedent for paying double had been set, we now have to pay extra (though not as much as double) on his trips too. It works out to an extra 33% per child to what the parents of DC's in 2-form entry years do.
I just crapped out and have DC in BOTH school years where we have to pay extra. 