I'm usually not fond of the pre-order culture, and wouldn't be pro this on a new AAA game as I'd prefer wait for a proper review, but the sudden release of a small DLC dungeon pack causes a sudden spike in the crown market. If their was an option to pre-purchase the Dungeon pack prior to its release this would ease the acquisition of the DLC and not mess with the crown market so much. Also allowing all players to play at launch rather than try to find a crown/gold trader after release.
Those with ESO+ have technically already pre-acquired it
Those without ESO+ will hammer the crown market on day 0
Those who don't care won't be phased either way