What, exactly, is the incentive in your hypothetical? Unlike DBCooper, I don’t expect that I will ever make millions of dollars. I’m pretty sure I’d be willing to make compromises to have access to that kind of money. In your scenario, however, it doesn’t sound like I’d really have access to the money. I’d be entirely dependent on the largess of the other party. To me, having a lot of money is good to the extent that it provides freedom. Having to ask for an allowance isn’t freedom.
Now, if you were to fill out the scenario by saying that this is a person who would make a good mother, is a kind person, wants me to pursue my own interests, and so on, it would be more interesting. Would I be willing to settle with someone I am not crazy about, but could be good friends with, could have children with, and would provide me with financial independence? Probably.
I also agree with imhungry that 10 million dollars is enough to be much more than comfortable. At 2% interest, that’s two hundred thousand per year, and one ought to be able to get much better average returns than that.