Okay, I don't agree with your calculations, that 10% extra put into work could also be a breakpoint for many jobs changing lives etc (very unreasonable, but that is the premise of your being nice argument), cause guess what, all those volunteer tasks that have compounding interests also can he jobs. A teacher that teaches 10% better could also change so many more.lives than your volunteer guy, a doctor working 10% better, literally saving 10% more lives.

I don't disagree that education and mental health impact the economy a lot, but I disagree on the magnitude you describe to these effects from chance meetings on the street etc from untrained volunteer workers compared to mental health professionals

P.s. saying yeah someone else does the job if you don't exist and then ignoring that argument for your own choices (like only you can do volunteer work and no one else) is kinda weird.