Their relation is alienated from the persons who form the relation, which is mediated by value. They become 'value-subjects', and those who possess enough value also rule the society. The Logic in fact describes the value-subject abstractly. In modern society there is wide-spread acceptance of the legitimacy of one person controlling the product of another's labour, and the other's labour itself, in order to appropriate a surplus product. This approval is founded on the value-relation and the 'form' of the commodity.
Value is abstract and imagined in the mind, and also embodied in money.
Hegel's Logic implicitly ascribes a sort of power to money, and Marx presents it as the demiurgos of bourgeois society. That is why he characterises the Logic as 'the money of the spirit'. His task in the Grundrisse therefore consists in demonstrating that the genesis of value and its development into capital are described in the Logic, albeit in a seemingly closed system which reproduces itself, and overall his work is directed towards transcending capitalism in practice.