Discounts if you own the previous title already exists for a very long time. I recieved several 10%-50% discounts for owning previous titles already. They are talking about bundles if you already own one or half of the games included.
If you look at how much work and effort they put into their games while still selling them for 40€ which basicly only some indie studios do these days, you really need to ask yourself if you would work for free. I personally would preffer some bonus for HoI III owners rather than an discount to be honest. (Victoria II to Hearts of Iron IV Converter pretty please

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Paradox games are already a much better value than most other AAA games at launch and have much more playability value to then. You essentially pay 40€ for a game that you can easiely play 1000 hours and more, while other companies milk you for 60€ (or even 120€ if you ask EA) for one game that dont even lasts 4 to 5 hours.
You need to keep in mind how much time and effort paradox puts into their games. Sure, in the past they released their games a bit too early and they had a rough start, but look at what they did with HoI IV. They delayed it for a unknown period until they are sure it is ready, which was over a year ago now. They are also patching and supporting their games for an insane amount of time. Then you have the optional expansions which also deliver a big free content patch aside from the paid content aswell, which greatly improve gameplay aswell. Sure, then you also have tons of completly optional cosmetic mini dlcs which are basicly there to keep their artists working once their work on the game itself is done and have absolutely no impact on the gameplay itself, so it is fine to not buy them if you dont want to.
Other than that dont let us forget how often they put their games and expansions on sale and how high those discounts are. And of course, for me, the most important aspect,
showing the game itself (no inengine or render nonsense) in its true gameplay form well before release and releasing demo versions of their games.
It is sad that some people only look at the number of dlc's a game has and dont even bother to look at what they are actually are and accusing Paradox for "milking their customers". This is not directed at you, but at the ignorant people out on the internet.