Crankin, I was in a similar situations some years back, and declined to go to the engagement party because I couldn't afford a gift. At the time I was pretty broke, due to only recently starting working again after prolonged unemployment, and I was pretty annoyed that I had to spend money to buy things for these people when I didn't own any of the things on their registry and couldn't afford to buy them for myself. I chose the two cheapest things on the list to give them.

(At their reception, one of the couples' very close friends had to leave early because he was sick. When someone told the bride he had left, she said, angrily, "well I hope he ate his dinner before he left because I paid a lot of money for it." Sometimes I really don't like weddings.)