In my region, it is customary for the guests to give an envelope to the newlyweds, with the sum of money somewhat approximating the marginal costs of the guests' presence on the event. That is, if all the guests were nice and following the custom, the newlyweds would have recouped a big part of their expenses. In other words, a modern wedding is basically a process of transferring significant amounts of money from the guests to the caterers, photographers and venue owners.
Capitalism at its best.