I have said no once before. Of course, a person needs to say no when they are first approached about it and not when plans have already been set...Which it doesn't sound like you're planning to ditch, just that you wish you would have said no.
One friend of mine got married and I was a bridesmaid and the dress was over $250...then, on top of it, she lived an airplane ride away- so add in hotels, rental car (we HAD to rent a car, we didn't have family or anything nearby), food for the weekend and she was a bridezilla, so she went as far as to telling us WHERE we were all staying, where we were all eating and what other things she expected us to spend money on. I was shocked with her being a bridezilla, but what ever.
Well, not being shocked about them getting divorced a year later because her husband was having an affair- she is getting re-married this October. HUGE wedding. HUGE. She asked me and both of my girls to be in it and I said no, immediately. I didn't need to spend another $2,000 on a weekend where no one got along with her and got yelled at by her and weren't respected.
If a person getting married expects large amounts of money to be spent by the wedding party, they should at least be respectful and polite about it...
her and I are still 'friends'. She's actually not that bad of a person other than going wedding crazy and getting 'wedding stupid'