Tell him you'll play at his funeral too but you want to get paid up front.
I work for a wedding planner, and I get paid to do weddings.
My brother played a wedding for a friend for free, and got a thank you note in the mail with $100 in it.
The best way for your frugal friend to have handled this would have been for him to say "How much do you usually charge for weddings?"
That would have given you the chance to say "I usually charge x but for you I'll do if for (free or reduced rate)." Too late for that now.
He should have sent a little green with the thank you note.