That is not so bad to depress some of those wages, my plumber is making $2k/Day. I don't know too many people making that kind of money even in tech, let alone other disciplines!
I know quite a few old ones and I know many many more who struggle with pain every day as they are my age and talk to me about it. ( IT being my 3rd career after welding and meatcutting ) I have many friends who are dropping out of the workforce and finding alternative jobs because they cant do the work.
Painting is hard work but its one of the less body impacting you can do. There are a few roles like that and yes, being active is a good thing.
In a similar vein, Apple takes in over $2,000,000 of revenue per employee, but Genius Bar employees are not taking that amount home. I mention this solely because it uses the same reasoning evident in your initial claims.
So yes... I think the average plumber in SF is making about $70k/yr. (so ~$300 per day worked, or $200 per day).