I think that's too simplistic. Paradox as a studio has a pool of programmers, artists, content designers and so on. It has been explained back in the "AI IS BROKEN" days that these people move from game to game as necessary, and if HoI4 happens to have someone capable of designing focus trees, then of course he is going to design focus trees. That's fairly straightforward.
On the other hand, it would be much more complicated for someone to untangle the web of focus trees and AI calculations that lead to Italy joining in 1939, tweak them in a way that still lets Italy join WW2 at some point, test these changes for a variety of relative faction strengths, and check that they don't lead to something completely unexpected like the German thinking they should invade Switzerland to bypass Maginot.
Add to that the designer next door may or may not be tweaking the formulas you are using, and it's probably something that only a few people could do at a few specific times.
Replace budget with man-hour from the total employees's pool and how they are spent if you wish. It is the same. Man-hours of work spent doing something and not another because of a design vision/decision.