Waves has been doing these firesale sales for many years now. Black friday is always the time of the year to buy into Waves stuff.
Frankly, they have reached market saturation. All of the professional studios and engineers already have most of their products and to keep selling new stuff to new customers, they have to lower their prices to the hobbyist and project studio level. And those people aren't going to lay our $3,000 for a plugin bundle. But a couple of hundred? Sure.
I haven't paid full retail prices for any Waves product since my first bundle back in 2004. And I have the Diamond bundle now and a bunch of other individual plugins. I may upgrade to Horizon this weekend if Audio Deluxe comes back with a killer deal.
BTW, if their last few years have been any indication, they will hold these prices through at least Cyber Monday, and maybe even longer.