I am sorry for you, and your friends are CFs. But I would never ever ever pay upfront for ANYTHING for other people.
I get/have got this quite often (and DH too.) He works at a place where he can get 30% off a certain thing (let's say, tickets for concerts/shows.) So 2 X £45 tickets (£90) would cost him £60, with his staff discount. So a decent discount.
At least once a month, he gets someone asking him to get 4 tickets for him for a certain show, (which he gets for example, for £120 instead of £180,) and they say 'get them for us and we'll give you the money back next payday/in 2 weeks.'
When people say this, you're chasing them for the bloody money for weeks, and you end up feeling bad for asking for your own money. DH (and me,) have had times where the people who owe us the money, start getting annoyed with us, and say ' I WILL give it you, I just don't have it this week like I thought I would,' with a
kind of look!
Needless to say, we have stopped doing it now, and refuse to get ANYthing unless they pay the money up front.
I agree with the posters saying you should tell them you are cancelling if they don't pay within 48 hours!