This thread has some historical sales numbers. Apparently some articles and reports get mixed up between reporting 24 hours sales and first week sales, so these might not actually be accurate
https://www.reddit.com/r/wow/comment...s_figures_and/
Vanilla:
240,000 in the first 24 hours.
The Burning Crusade
2.4 million within the first 24 hours
3.5 million within the month
Wrath of the Lich King
2.8 million within the first 24 hours
Cataclysm
3.3 million within the first 24 hours
4.7 million within the month
Mists of Panderia
2.7 million within the first week
Warlords of Draenor
3.3 million in the first 24 hours
https://en.wikipedia.org/wiki/World_..._Draenor#Sales
Legion:
3.3 million in the first 24 hours
https://www.gamespot.com/articles/wo.../1100-6443409/