Why is it that giving money to rich people increases their motivation, but giving money to poor people decreases their motivation? This "motivation" thing sure is hard to understand!
People are on a continuum between "extremely lazy" and "extremely hard-working". I know that I would stop working if I had ten million dollars, even though I love programming, because I would prefer to read books all day long. Elon Musk, on the other hand, would probably not stop working even with ten billion dollars, because he is obsessed with creating stuff.
This suggests that most people will generally settle where they are content with what they're making. I know this is true for me (it would be easy for me to make twice what I'm making now, and ten times is achievable but would take a lot more effort than I'm willing to put in); from what I can tell, it's true for all the people I know.
Also, you're equivocating on the "giving money" expression. Giving $10 to a homeless person and to Elon Musk would probably not motivate either of them.
