The friendship should remain affordable even when its members’ incomes grow apart.

Money changes what a shared plan costs before anyone talks about it. When one person’s restaurants and trips quietly become the default, the other has to choose between spending badly and explaining why they cannot, and most people will simply start being busy instead. Friendships more often end that way than in any argument about money.

Keep some of what you do together cheap enough that nobody has to think about it: a walk, a kitchen table, a coffee. Suggest those without framing them as an accommodation. If you are the one earning more, propose the inexpensive plan first so the other person never has to.