For myself, I would regard those gains to be sufficiently small that I would think it irrational for an egoist to focus much of their attention on earning more money at that point, rather than fostering strong relationships, a sense of purpose, or improving their self-talk.
I agree with this.
The main takeaway I’m pushing here is something like:
“After a certain point, making more money has severe diminishing returns re: your happiness, as does donating lots of money.
So don’t lean on making lots of money to make you happy, and don’t lean on giving away lots of money to make you happy.”
There’s a temptation to use “donate a lot of money to effective causes” to scratch the “sense of purpose” itch, which I don’t think works very well (due to the diminishing returns).