At a good friend’s wedding a number of us were invited to attend the reception after the meal, just before the band was due to start, because they had limited funds. I thought it was a good way to include us without blowing the budget.

Edit: I should add that, if you have a wedding in a church or a public place, anyone can attend the official bit, and I have been at weddings where randoms turn up for the church service and sit at the back.