Stellaris II: I, For One, Welcome Our New Robot Fungus Hivemind Overlords

[Olinser]

the increased base income makes it less bad sure, but even that early snowball barely makes up for paying 50% more for most of your Mining stations than you otherwise would have had

The mining station tradition was not good to begin with, which is why they changed it. It was a pretty mediocre pick as the absolute FIRST pick you took, and if you took it at anything other than first pick it was one of the worst picks in the game, the buff was effectively useless and not even noticeable.

By the time you get your first tradition you've built most of the initial mining stations you can reach anyway. The paltry mineral reduction cost on stations was simply outshone by half the other traditions in the game as a first pick, even more now that you have more initial mineral income.

15% cost reduction on ships and buildings is much, MUCH better than mining stations at basically every stage of the game and is actually one of the better end game buffs now. '50% more for mining stations' is a really fancy way of saying '30 minerals more'.