> I noticed often in couples, there is one with money and one without.
Where did you "notice" this exactly? Because this is false. People tend to mate according to similarity of socioeconomic class. That means similarity of economic class. Cultural factors (the "socio" in "socioeconomic") are also important and correlate with economic factors. Greater similarly of cultural factors and economic factors creates greater opportunity and affordances for pairing. There's a greater common ground to work with. You're not going to find many classically educated billionaires married to barely literate burger flippers.
> I guess this is out of necessity and it satisfies both the poorer person's need for sustenance and the richer person's need for control over the relationship.
I don't know what bizarro world you live in, but this is not the general case. Again, people tend to mate according to socioeconomic similarity. That means both are earning within a similar-ish range or some from families with similar socioeconomic characteristics. The only way you can conceivably control someone in this manner is not to out-earn them, but the one earning less must earn less than needed to survive, have no realistic prospect of providing for themselves, and have no family or friends he or she can rely on. Telling someone you'll take away their Birkin bag isn't much of a threat to a poor person; starvation is. Your view of what most marriages are like is, frankly, delusional and dark, like something from an incel forum.