It's simply a supply/demand situation. The demand for exclusive holiday fare is greater than they can provide. So, by making it a special event, they fill the demand. Tickets sell, and as stated above, it seems they sell well.
If it continues, will there be bigger and better events for upcoming seasons? More live holiday shows, etc?
i thought to myself, Halloween time, sounds fun... But I saw the upcharge and went to DCA.
NOW, if I was a parent, I might have bought tickets.
I am all for meeting the demand. Am I sad there's a separate charge? My wallet is, but if I want to go, I will pay.