Earlier quoted context omitted.
Unless GP is close to destitute, bickering over spending $400 on their primary tool that presumably keeps them gainfully employed is the literal definition of micromanagement. I do have a partner and she has autonomy over the money we earn together as do I, because we trust each other to make reasonable decisions.
You can't both have autonomy over the same resource. It sounds like you and your partner have a mutual understanding of the other's spending, and your expenses are low enough and/or your income is high enough that it doesn't create problems when you spend below the implicit limits. That's great for you, but it comes across as narrow-minded to talk as though a $400 expense is unworthy of discussion to every couple.
“Unworthy of discussion” vs. “isn’t going to be happy” is a good way to move the goalposts.
I suppose I’m just tired of the juvenile meme of “my wallet is going to hurt” or “my wife [almost always wife, and never husband; what does that say?] is going to be upset” at .
If that’s the level of trust one has in their life partner, one ought to take a closer look at what’s really important to oneself.