> Unfortunately, much if not most of the time this calculation by the worker will be in error. As they tend to exclude the company scaffolding that they are not responsible for but that enables them to make their contribution.
I literally addressed that "company scaffolding" in more detail than you do here (second sentence of the second paragraph). There's no error here though as running the company and owning the company are two different things and while there are plenty of business owners who need to work for their own company to keep it running, we're specifically talking about surplus value after the cost of paying all labor (including your own, at market rate), i.e. what ends up either being reinvested at the end of the fiscal year or drained by the owners/shareholders as dividends. You may need someone to run the business side of things, you don't need that person to also own the company, be able to drain any profits and fire you at will.
> If group ownership is important, workers can certainly begin a business with that in mind.
We like to proudly talk about individualism when it comes to seeking praise for personal achievements but times like this demonstrate how it can blind us to systems thinking. Yes, you can create a worker cooperative. And yes, you can be a business owner who tries to be "fair" to their workers. But you exist in competition with other businesses who don't engage in such "waste" and you compete in a system where the "benefits" of such an approach are considered externalities and have no direct value (even if you try to argue it's "positive PR" that will only get you so far). In other words, the system disincentivizes and actively punishes redistributing surplus value to your (co-)workers - because it's literally based on profit-seeking (i.e. maximizing that surplus).
> Asset ownership being the key to legal and ethical economic success in this world.
Yes, and asset ownership is only attainable if you have the necessary capital to buy assets. Being self-employed won't get you far because you're still selling your labor for money (just with fewer middlemen but in practice not really) and if everyone owned their own business that's all they'd accomplish. If you want to be economically successful from asset ownership rather than labor, you want your "asset" to "do the work for you" (i.e. passive income). But in real-world terms this ultimately means you need to get a cut (i.e. profit) from someone else's labor (and they therefore can't take this advice or else they wouldn't be in that position for you).
I'm a business owner. I've been at various stages self-employed, an employer and a business owner using external freelancers and subcontractors. But I have no illusions that essentially the easiest "legal and ethical" economic success I've seen involved little more than either rent seeking (i.e. being paid for continuous usage of something you already built/bought) or scalping (i.e. selling something someone else made/did at an inflated price and pocketing the difference).