On mistresses and toyboys
When rich men leave their aging wives for younger women, they are not recognised as responding to incentives, but considered as acting unethically in a vacuum. Right-thinking women are indignant, unless of course they themselves are the ones who get to replace those aging wives; and even otherwise, no right-thinking women would dream of condemning the younger women for making the abandonment possible. That would be an antediluvian and unsisterly response.
And let’s not talk about the rate of replacement for toy-boys. What, you say? Is keeping a younger sex partner rational behaviour in a lonely rich woman? Then it is rational behaviour in a lonely rich man.