It seems connected to one of those issues people are super reluctant to actually look at when they form relationships: "Are we financially compatible?"

Finances often reveal parts of personality — along with psychological issues — we don't really get to see in other ways. Sometimes what's happening is someone trying to "fill an empty space inside" by acquiring things that will never fill that space... and the empty space is about old trauma, not even about the current relationship.

Yes, I've experienced variations.

My ex was an uncontrolled spendthrift who ran up some US $60K in consumer debt. Interestingly enough, she was very capable of managing and living on "no money" when we met, but her "retail therapy" ramped up at a much faster pace than our income rose. The woman I was in a multi-year relationship with subsequently very openly admitted to being "stupid with money" and I should have recognized that as a warning sign... she pretty much "impulsed" everything in her life in the moment never pausing to even consider that the money had to come from somewhere. She was a senior engineer in the IT industry and just knew she had a 6-figure income *(USD, 1990s) and that "should be enough" to get her whatever she pointed at. In a sense, it was "revenge spending" against a childhood where her parents had money but refused to ever buy anything.

All just goes to show that the Human Psyche is a strange place.