The point is the legal benefits and publicly declaring your love and commitment, if you care about that.

You can spend as little as you want, if you only care about the legal status. But since you are probably asking about the usual big wedding - it’s really just throwing a party to celebrate the act. It’s not mandatory. Invite people you want to party with and celebrate life in a way you want.

What can suck about it is the peer pressure from parents and other people to do it the way they want, to do it “properly”.