No metaphor. My point is that there is no literal value. If people did not value gold for its rarity and aesthetics, it would have been a nearly worthless material until we discovered electricity. But rarity and aesthetic preference made for scarcity and desirability, making it valuable.
There is no literal value. The labor you put in adds to what you consider the worth of the work to be, but it matters not a whit to the person who buys the result from you; he only cares about the result. This push and pull between whether you're willing to put in the labor in exchange for what he's offering, and whether he's willing to offer what you ask in exchange for the product of your labor, is the only value your labor has.
In fact, most of what people count as "profit" is actually the labor. It's the part that is "above" the "material cost." And the material cost is yet defined as "what it cost the manufacturer to acquire the materials." This price, too, fluctuates based on scarcity of the material and the amount of labor the material-acquisition service was willing to put forth for X amount of profit above THEIR material/overhead costs (whatever those may be).
Demand is all that matters. Not "demand for the product" alone, mind, but demand for the product vs. demand for the currency. Remember that "money" is just a fungible abstract representation of goods and services bartered back and forth. It has no intrinsic value other than whatever material it's made of, and even that is inconstant because...well, let's say that we had "gold standard" currency for a moment: if $1 bought .01 oz of gold because it was literally a receipt saying you owned .01 oz of gold, and suddenly somebody found a way to produce gold out of thin air with practically no effort nor material input at all, the value of the currency would plummet instantly as everybody could get gold trivially.
Supply and Demand are the only things that determine value. Supply by dictating how much there is to go around, and demand by dictating how much somebody would part with in order to get part of the supply. This includes labor. Labor is something that is in supply and in demand. How badly it is in demand vs. how much of it is in supply determines how much somebody will pay for it and how much somebody will TAKE for it.