And when I need welding services I call around, get quotes for $30/hr and $40/hr, and support the business that has minimized costs and passed the savings on to me, because that's how competition works.

You might be willing to spend more money on a business that you know pays employees better (even if you get exactly the same service from them). If there are enough customers like you, a business can get some market advantage with a pro-employee reputation.

I doubt there are many such customers. The most vocal critics of Amazon on Hubski are also Prime members, paying $139 a year for the privilege of patronizing Bezos. They even admit that low prices are a reason they overlook their scruples, as if low prices and minimizing labor costs are completely unrelated.

I shop at Trader Joe's all the time. I believe staff there is well-compensated; they seem loyal as I see the same faces week after week. I look for two francophone workers and try to chat with them. Their compensation costs more than what they would get at Walmart, and that extra compensation comes out of my pocket, obviously. I have a comfortable budget for groceries, so I am willing to pay more for the pleasant atmosphere. If my budget were tighter, I would save money by giving up on charming staff and shopping elsewhere.