Can't speak for the traditional December 25th Christmas dinner as I married into a Catholic family so "Christmas" for us is always Christmas Eve on the 24th; December 25th is for sleeping in and recovering, and resting, and watching TV, rinse, repeat. Several times.
That said I did have a wonderful brunch with my sister and BIL and that side of (his) family at the Bear Mtn Westin hotel this morning. Lovely setting, recently remodelled space and very busy by about 11am. Perhaps 80-85% capacity. All I can really say is that I cannot imagine what Christmas dinner must be costing these days because the brunch was $100 plus grat.
Buffets of course are generally not a great value proposition because no one can actually eat $50 or $75 or $100 worth of food but "damn" the world is getting expensive. Several years ago we actually did do an extended family December 25th dinner because we had too many people, about nineteen, to seat in a house so we went to the Marriott hotel downtown; this was about 2010 and I believe the cost per head then was about $60.