wedding supplier charges

Do Suppliers Charge More for Weddings? I once read a post in a forum put there by a prospective bride. She was complaining, with some bitterness, that when suppliers hear the word wedding they see it as a cue to double or triple their prices. A claim that sparked quite some discussion. But is it true? Do caterers, cake-makers, venue dressers and photographers etc hike their prices at the very mention of the wedding word? And if they do - are there any good reasons why suppliers charge more for weddings?