K, soz, but, I don't get what you mean, anon: The construction of a chair takes X labor time. Under capitalism the need to exchange arises due the material processes of the system historically: Division of labor and monopolization of commodities. The capitalist exchanges a portion of his capital in the form of a wage to a worker for the production of more capital. in this case chairs. A whole process arises outside of the realm of the specific utility of the commodity in which in order for an exchange to take place there must be an equivalency between two commodities: 1 ton of rice for 1 ton of wheat, 1 ton of grain for 1 ton hay, 1 ton of x for 1 ton of y, 1 hundred dollars for 1 ton of x.
The point I am making here and the point Marx was trying to get at is that, through all of this, the actual labor it takes to make a chair does not change during that point in time. Over time it my change due to technological advancement, but, that is irrelevant for now. Right now it takes X amount of labor to construct a chair; we measure this labor in the form of time, or, labor time.
Ergo, a chair and its production will always be X meaning X is the value of the chair. Now, take something like diamonds, for example, it takes much much more abstract labor time, to produce one diamond than it does a chair. You have to get people to work in a quary for days and days on end to only, possibly, turn up one diamond.
Hence scarcity, thus the value of the diamond is much higher than that of a chair. All assuming that both are produced at the socially necessary standard of labor which is another can of worms all together. Sorry I didn't mean to be a dick I am just really hung over.