Yes you are correct I am arguing from what is the best way to behave within a market system and you are also correct that a market system is not the best way to organise society but as it is the current way we organise our society it's worth considering how to live in it

Yes trade unions won't on their own result in communism

operating in the market competitatively is stupid for anyone. It's like paying double whatever the person you're negotiating with was asking