& I read this on Leninushka's blog, as an explanation of Karl Marx's notion of surplus value:
"Let us recall the gist of Marx's notion of exploitation: exploitation is not simply opposed to justice - Marx's point is not that workers are exploited because they are not paid the full value of their work. The central thesis of Marx's notion of 'surplus-value' is that a worker is exploited even when he is 'fully paid'; exploitation is thus not opposed to the 'just' equivalent exchange; it functions, rather, as its point of inherent exception - there is one commodity (the workforce) which is exploited precisely when it is 'paid its full value'. (The further point not to be missed is that the production of this excess is strictly equivalent to the universalization of the exchange-function: the moment the exchange-function is universalized - that is, the moment it becomes the structuring principle of the whole of economic life - the exception emerges, since at this point the workforce itself becomes a commodity exchanged on the market. Marx in effect announces here the Lacanian notion of the Universal which involves a constitutive exception.) The basic premise of symptomal reading is thus that every ideological universality necessarily gives rise to a particular 'extimate' element, to an element which - precisely as an inherent, necessary product of the process designated by the universality - simultaneously undermines it: the symptom is an example which subverts the Universal whose example it is."
(from Dr Žižek's Ticklish Subject)
According to Marx's theory, as laid out in Capital, the remuneration of the predominant form of labour, disqualified or undifferentiated labour, sold on the open market and so remunerated its "true" market value will tend to a conventional minimum, just enough to reproduce the worker as worker. The product of labour will likewise be remunerated its value as realised on the open market, which according to Marx, following the example of Ricardo, will be equivalent to the value of the labour of which it is comprised. Surplus value, which accrues to the capitalist, represents the difference of these amounts.
According to Baran and Sweezy's definition, surplus value is "the difference between total social output and the socially necessary costs of producing it", theoretically this could apply to situations other than that described by Marx.
This theory is eminently criticiseable, (though professional economists tend to prefer to ignore it altogether). Nitzan and Bichler describe the labour theory of value, where labour produces its value but is paid the value of its own production as "a dangerously circular notion". Certainly one wonders why the value of each commodity isn't bid down by "competitive markets" to the value of reproducing productive labour, so value added by labour equals the remuneration of labour and the neoclassical model holds*.
Karl Korsch supposed that the laws of motion of the capitalist system disclosed by Marx's model were evidently correct but that the presupposition underlying it should realistically be conditions of monopoly rather than pure competition (Sweezy concurred with this view). The tendency of capitalists to not compete on price would be a consequence of (a high degree of) monopoly, all other conditions would hold.
The crucial advance of Marx's theory over that of the economists of his time, and which their successors have conspicuously failed to make good, is to describe a dynamic economy in which both the remuneration of labour and capital are "real" outputs.
Žižek's reading of Marx, which to be fair to its context, is surely meant to be an "against the grain" piece of belle-lettrism, sets up an integral ambiguity on the phrase:
"the full value of their work"
which could mean either:
"the full value of the remuneration of their work"
or "the full value of the product of their work"
and "justice" could mean
"the most equitable"
or "according to the law"
...hence there's a number of meanings suggested here that seem more exciting than the only one that can be reconciled with what Marx writes in Capital: that workers are paid the going rate and that this is in accordance with the law of the land. This contrivance of ambiguity where none is necessary compliments and reinforces what one supposes to be the background impression of Marx and his work as evoked through the wider cultural and educational apparatus, as fundamentally ambivalent, both validated and discredited. This ambivalence seems to be often indicated, where our ideology "crystallises" into the form of the individual. And it is surely in this respect that Marx announces Lacan.
*The objection to neoclassical economics here seems to run something like this: while one business or one business sector could reduce its prices to merely cover inputs, this behaviour can't be aggregated to the level of the whole economy since price cuts are only relative price cuts (some players gain, some lose) and don't have the effect of lowering total output, while neoclassical economics considers the lowering of prices to be consistant with output being added to.