Yes, every time they announce that they’re a vegan they get their payment in the form of a hit of endorphins. That’s why they do it. Pure smugness. Which you’d know all about.
So now you've shifted your position from being paid to do something (in your example, with money), to doing something for the neurochemical reward. That's a big shift, whether you want to acknowledge it or not. It's still wrong, of course, but it's a massive goalpost move.
Your shifted goalpost is significantly harder to argue with, because while I'm sure there are vegans and vegetarians who became such for reasons other than dopamine, that's a very difficult thing to prove. So instead, I'll give you an example of someone who did something which definitely did not get him a hit of dopamine or money.
en.wikipedia.org
Valvilov was a scientist who refused to bend his scientific efforts to end the famine in Russia, even though he knew it would land him imprisoned and ultimately executed under Stalin. He was starved to death in prison for his valor.
en.wikipedia.org
Giordano Bruno was burned at the stake for his scientific findings, which he refused to recant.
I'd expect by this point that you realize that I could fill this page with people who faced persecution for their beliefs, or who committed acts of valor on the battlefield, each of whom would have been doing something for reasons other than payment OR dopamine. And I'd expect that at this point that you'd realize that almost everyone has something they'd be willing to make deep personal sacrifices for, despite a lack of any kind of monetary or chemical reward, simply because they used their intellect to sort out what it was worth and why. I'd expect that, but I'm spelling it out here because I expected it in the previous post.