I have booked plane tickets, 6 nights in a hotel room and a car rental for a wedding in California in November. The plane tickets are non-refundable but I think I may be able to make a change for a cost. If the wedding is cancelled in the next month, I will have a decision to make: (1) go anyway, it's a touristy place that I've never been and maybe DH and I will enjoy it or (2) cancel the (very, very expensive) hotel rooms and car rental and use the tickets for something else (at a cost). Option 2 is likely what we would do since we could use the tickets to go see family or other friends and the touristy place (while lovely I'm sure) is not really our cup of tea anyway. And, I avoid the large costs associated with the room and the meals and the car and everything else. So, I would be out some money on changing the plane tickets, but it would be way, way less expensive than actually going on the trip.
What I absolutely cannot imagine is if I were to go anyway and then expect the bride and groom to throw me some kind of an event while I'm there. I mean, really? If I am spending a pile of money on travelling to a wedding, it is because one of the HC is very close to me. I'm not going for the meal and the DJ/band, I'm going for the wedding. And if the wedding doesn't happen, I'm not going to ask these close friends/family of mine to pony up a supper anyway.