Unless you're lucky to catch one of the moments when the DLC is mega-cheap (e.g. 'This is an affordable way for players to experience the entire Crusader Kings II catalog without having to weigh which items they would prefer to purchase.' 'With so much additional content available, the cost for new Crusader Kings II players can seem prohibitive or intimidating,' Paradox explain in the announcement. Some bits are better than others, and some are just decorative, but it'll all be there for subs.
The subscription service gives access to 13 expansions, 12 unit packs, 14 music packs, 10 portrait packs, the Ruler Designer, and the Game Converter which exports saves to Europa Universalis IV. They are still selling DLC separately the old-fashioned way, mind. Given that the base game is free these days, yeah, not a huge surprise. Alternatively, you now have the option to pay £4 a month to get access to all the dynasty-building RPG's DLC, thanks to a new subscription service Paradox launched yesterday. If you wanted all the expansions and content packs for Crusader Kings 2, at MSRP you'd be paying over £200.
