Interesting thread.
I don't think you can necessarily correlate spending on a wedding with the likelihood of divorce though.
We are spending about £20k on our wedding. About 75% of that is on food and drink. £20k is a lot of money but it's well within our budget. We fell in love with another venue but after getting quotes from the caterers, marquee suppliers etc and adding everything up we realised it would cost over £35k. That would have been within our budget too (in the sense that we could pay for it without having to get into debt) but we thought it was an unreasonable amount to spend on one day. We are really looking forward to the day and quite comfortable with the amount we are spending.
But £20k could be an enormous, unattainable sum for some people, who would certainly have to get into debt to pay for it, and a drop in the ocean and a "cheap wedding" for other people.
There's probably some truth in saying that people who are completely focused on the wedding and not the marriage are less likely to last. And I'm sure that getting into a lot of debt for something that is completely gone the day after your wedding and all you have left is an expensive dress and your memories could cause quite a lot of tension, especially if the couple weren't both completely on the same wavelength about the kind of wedding they wanted and could afford.
I know someone whose first marriage lasted six weeks. I have no idea how flashy or expensive the wedding was, but I do know that she rushed down the aisle with an unsuitable partner because all her friends were getting married and having babies and she thought that if she didn't do it before she turned 30 she'd be left on the shelf. She's now happily married to someone else.
I think if you choose to marry the right person for the right reasons and you see your relationship as a continually evolving thing that you have to work at, your marriage stands a good chance of success, whether you had a cheap registry office do or a massive swanky £50k party. If you're marrying the right person for the right reasons and you both want to spend a lot of money on a big party for all your family and friends and you can afford to do it, you should do it. You're (hopefully) only going to do it once.