In the spirit of the season, Paradox have released free DLC “Songs of Yuletide” for both Crusader Kings II and Europa Universalis IV. You’ll have to install them via the Steam store, but they are 100% free of charge.
Crusader Kings II is a Daily Deal today on Steam. At 75% off, it’s $10 for the the base game and $20 for the CKII Collection, which I think includes all the DLC except for the latest one “Sons of Abraham”.
Rats. I want that last DLC. I just got the pagan one recently, and haven’t used it too much, as I have a pretty solid run going in Ironman with Poland/the Wendish Empire.
I’m sure Sons of Abraham will be discounted soon enough. Probably during the Spring Sale.
That’s what I’m thinking/hoping. By that time, they’ll have another bit of DLC out there too.
Conquest of Paradise, the EUIV DLC with a randomized New World and expanded first nations tech tree/behaviours is available for preorder.
I mean, if you’re a weak willed person unable to not pay Paradox - like me. 
I see that Paradox are continuing the CKII model of releasing some cosmetic DLC along with the gameplay-changing DLC. I’ll probably pick them all up in some future Steam sale.
The base game of Crusader Kings 2 is currently (until Thursday) 75% off. And all the older DLCs are also 75% off.
The latest DLC (still full price) lets you play as a ruler on the Indian subcontinent. But even if you don’t get that DLC, the map has been extended that way for everyone.
I seem to have picked up the “Sons of Abraham” DLC at some point. I don’t even remember getting it! Since I haven’t cracked open CKII in months, I guess I can wait to get the latest “Rajahs of India” DLC.