I have three boys, so not sure what the etiquette is now. Of course, it used to be the bride's parents paid for most things, and the groom's parents paid for the drinks. That was how it was 22 years ago when I got hitched anyway, at least that seemed to be the "norm".
B#gger the etiquette - our three darling girls have been told that our contribution is a ladder ... so they can elope!
Hubby and I paid for our own wedding (30 years ago), so there's no reason they can't do the same!
Cheers
Lynn