I've stopped doing them....
Even if they cost £1.50 for contents and you have 10, that's blinkin' £15! But its easy to spend more than that. And have more kids at party
They are invariably filled with crap that is disgarded by child onto pile of discarded crap at home
They are pointless, a needless expense, and irritating
Do you do them? What do you put in them? How much does it cost you?