Concrete, real labor makes use-values. "Abstract labor" (labor considered as a social average, abstracted away from it's concrete properties, degree of skill, individual intensity, etc.) makes "value". Commodities in exchange have many exchange-values. A bushel of corn trades for a yard of linen but also for a pound of salt. Commodities in exchange with the money commodity have a specific exchange-value ("price").
The exchange-value of commodities is based on their value. The use-value of commodities doesn't play at all except as a precondition to them becoming commodities in the first place (without "usefulness", they would not be "exchanged").
The social engine of Capital is driven by a single trait: the cost of labor (wages) and the value that labor produces are of two different magnitudes. The price of labor is the cost of its reproduction. The only complicating factor is that we describe "reproduction" in social terms. It does not necessarily coincide with "simple reproduction" in the basest physical terms. There are a set of factors for producing labor of a certain intensity and there are additional historical, political, and social factors which help to determine its "price" at any given moment and in any given locale (country), as well.
The difference between the value of the commodities produced and the cost of labor is surplus-value. The "cost of capital" doesn't count at all here because capital is merely the "dead labor" of the past come to life again as the "means of production". In the capitalist system, surplus-value is created in production but realized in circulation, in the form of profit, interest, and rent.
Nothing that I have said above is even remotely controversial, from a scientific or a historical standpoint (until later, that is). When Marx writes about this, he nearly perfectly mimics Ricardo who in turn more generally follows Smith. Marx is simply much more precise on abstract/concrete labor and use-value/value, and MUCH more precise and accurate (as might be expected) when it comes to surplus value. The rest of Capital is very much a re-derivation of the fundamentals of Political Economy based on this more precise underpinning. It is on this basis alone that those who want to "debunk" Marx, invariably find themselves at odds with "Classical Political Economy" as a whole.
Interestingly, the elements of "Classical Political Economy"are fairly well known even prior to Adam Smith. Quesnay certainly understands them in part. So does Ibn Khaldun, who I quoted at length on PopIndy. So do a whole raft of medieval and ancient scholars (not the least of whom is Aristotle). In fact, the basic understanding of this, in its component parts, is arguably understood and explained at the very beginning of human history (written history, that is).
The complicating factor, historically, is that the dominance of surplus-value is a relatively recent form of expropriation. The precondition is obvious and is identical to the "dawn of civilization" (pyramids don't get built by those merely sustaining themselves): human beings must be able to produce more than it takes to reproduce themselves, and the incidental "trade", which reaches well back into the million years of human existence, must become regular and routine enough to transform use-values in "surplus" of one type into a range of use-values. Both of those come with agriculture and with "animal husbandry" in particular. Given that, the rest is a given.
For a million years of human history, captives are either killed or adopted into the tribe. There is simply no basis for anything else. With the dawn of the herds, however, the Greeks, for one, take no time at all to see "surplus product" in potential. The social innovation is a third status for boys captured in war (with "war" about to be waged for the express purpose of capturing people). The herd-boys become "slaves", who work to maintain and increase the herds but have no call on the surplus that is produced. Social property is the innovation and its first fruits are class society (slaves and "free"), which in turn nearly immediately transforms itself into a society of several classes (slaves, women, freemen, slaveholders). For our immediate purpose, the form of expropriation is surplus-product. Though it appears that the slave is "owned", body and soul, nevertheless it is only the surplus-product of the slaves which is expropriated - otherwise slavery would die with the slaves in a single generation. Here, the expropriation of surplus-product is masked by the property relationship of the slave to the slave-master.
In Feudal times, the absolute ownership of one human being by another is largely superceded by serfdom or a free-holding peasantry in which the primary form of expropriation is as surplus-labor, with each producer obliged to contribute so many days of labor per year on the lands of their Lords and of the Church. The unending battle over "how much to each" tends to mask the fact that it is again feudal property that is the basis for extracting only surplus-labor (otherwise, feudalism would last only a single generation).
In our own times, of course, we have free labor which is free of all means of production and thus free to sell itself by the hour, not to one expropriator, but to any expropriator of their own choosing, provided that it occurs at the "prevailing rate". Here, the labor is paid for, "in full", at the point of production, but surplus-value accrues, as if by magic, only in circulation. The capitalist property relation appears in the ownership of the surplus products of labor transformed into commodities themselves.
The extraction of "surplus" is the same but property relationships, how they are masked, and which point in the process they appear are all fundamentally different (so too, things as, "basic" as for example, "fundamental human nature", are vastly different as well).
The point of this last is to simply understand the context of "value", "exchange-value", "use-value", and "surplus-value".
