I find that weird, xenonauts 2 tactical is super easy compared to other games of the genre, especially xenonauts 1, here's why:
You misunderstood, this would BUFF the money, especially on lower difficulties like soldier. It would only slightly decrease it on commander, which is the highest difficulty
I'm playing on commander/ironman (technically honestman because I don't want my save bricked due to bugs), and i find the funds to be pretty plentiful on that difficulty as is.
the game IS balanced around ironman, it's very ironman friendly. I suggested rescaling the funds because the funds being stingy is a pretty common complaint, you literally said it's stingy in your post.