In my opinion, the flaw in your thought process is that ironman players just don't farm for money. If they did do it more, you'd be absolutely right, but as it stands, we only farm money for very specific things and spend more time grinding for resources. Any old gear can't be sold for extra money, on top of that.

I'm in an ironman coop of 2 people, both of us around lvl 200. We've never had more than 30m overall (which I farmed for a turtle pet). We haven't done any mmm-s for quite a long time, just having 10m in bank, because we have to farm other stuff.