I don't think it makes much sense to assume that all of what's not "surplus value" (the "due" return of capital, I take it?) is already captured by labor, which

I don't think it makes much sense to assume that all of what's not "surplus value" (the "due" return of capital, I take it?) is already captured by labor, which is what the claim that all the value one creates over one's compensation is "provided by [...] the people who built the company" means, I'm pretty sure. In fact I think things get pretty messy and unhelpful when we start trying to attribute the "proper" due of anyone involved in this. You get what you get, and if your employer's not getting more than that they should probably look at hiring someone else, and if they could pay you less for exactly the same return on your labor they absolutely would, even though the value you're creating is the same, which tells me that no, capital is not somehow responsible for all that extra value, and I don't think it makes much sense to put things in those terms, even—like workers, they just get whatever they can manage to get. [EDIT] point remains, your wage is the cost of having that work done by labor in the market, unrelated to the value (return on investment, say) it provides, except that same value puts a de facto cap on the wage. If capital can get a 10% return paying $20/hr, they'll do it. If they could find a way to do the exact same thing but pay $10/hr, they would. "Value" remains constant.