The issue with PDX is the total cost can get too high and, I assume, pushes away new purchases. If you play one of their games and buy the DLC as it comes, it's fairly cheap. The base games are a fair $40, which is nice. However, to catch up on HoI4, which I think i purchased the deluxe edition for, would cost me about $115, while most of it is 50% off right now. Admittedly a lot of this is cosmetic stuff that could be skipped, but the price has to scare away new players. EUIV is $248 for me, with most between 30-70% off. Even CK2, which I own every expansion for, is $157 for cosmetics, content packs, music, etc all 50% off. It gets ridiculous.

Personally, I tend to buy these games at launch and, if I want to play them a few years later, I pirate it. I have given Paradox a lot of money and I like supporting their games, but I play far too many of them (basically all of them) for me to think it's reasonable to buy all these DLCs. I'll buy the first couple, but after that I'm probably never putting the time into it like I did at launch and it isn't worth it. Piracy becomes the most convenient option at that point, as long as you don't care about achievements.

I don't really mind this model because it seems to work for them, and it let's them continue to work on a game for a decade or more, instead of being forced to start from scratch and remake everything over and over. I know I'm not the only one doing what I do though, and I'm sure they know this as well. You don't need the expansions and everything, and they even include parts of it for free usually, but some mods will require them or it would just enhance the experience I already payed $100+ for, so I like to use them, but just can't justify the price for the 5 PDX games in active development plus the other studios games with the same model, like Cities: Skylines.