What's normal? My DD and SIL were married by a judge and for their 10th anniversary had a big wedding--with the two kids involved. It was really cool. My sister and her DH renewed their vows at some point, I can't remember which year for them, but it was a much smaller do. There weren't presents at either of these. For whatever reason, it might be that they want a big party, they've chosen this way to commemorate their marriage. Do I understand it? Nope. My idea of the perfect wedding would be a very small number of people involved and low key.
I should never overestimate my basic arithmetic skills.