Caitlin Kenny looks into why wedding dresses are so expensive and ends up concluding it's because people are willing to pay a lot for them: "Spending a lot on a wedding dress is a way for the bride to tell the world, 'I'm only going to do this once, so I'm doing it big.'"
A related issue, which I think does a slightly better job of illustrating exactly how exorbitant wedding spending can get, is the positional competition element. Nobody wants to have a below-average wedding or a below-average wedding dress. If you're a reasonably prosperous person with some discretionary income, what you'd like to do is figure out what it's "normal" to spend and then spend a little bit more than that. Do anything less and you're a cheapskate. The problem, of course, is that we can't all be above average so wedding spending keeps increasing faster than inflation. You can see the dynamic at work pretty clearly if you look at a poor country like Indonesia where overall material living standards are much lower. People have less money so they suffer in various ways -- smaller houses, fewer cars and appliances per capita, less vacation travel. But they don't enjoy their weddings and other family celebrations less, even though they're spending a pittance by American standards. The spending is driven by relative considerations, and the comparison class is (relatively) local. The richer a country gets, the more resources people have available to spend keeping up