“A+B has less exchange-value, because its exchange-value now exists only in relation to C, D, E, F. But the total of A, B, C, D, E, F has no exchange-value at all, because it expresses no relation.” (p 208)
The conclusion Ganilh draws from this is entirely Mercantilist. He says,
““Hence it is that it is difficult, and perhaps impossible, for a country to enrich itself by internal commerce. It is not at all the same for peoples who engage in foreign trade” (l.c., p. 109).” (p 209)
Wealth here is associated with the accumulation of money, and value is not labour. Value, in essence, becomes surplus value. A society becomes wealthy because it produces more value, but this value results not from labour, but from an unequal exchange. Its this Mercantilist view that some Third Worldist and "Marxist" economists have presented to explain the accumulation of wealth in developed, "imperialist" economies. They explain this accumulation of wealth as resulting from relations of "unequal exchange" between these "imperialist" economies, and the less developed, or worse "under-developed" economies that results in a so called "super-exploitation" of the latter. These Mercantilist explanations of the success and wealth of the developed economies are framed in a variety of theories concerning colonialism and neocolonialism, and so called "centre-periphery" relations.
“Value consists in my getting not an equivalent, but more than the equivalent. At the same time, however, for Ganilh there is no equivalent, for this would imply that the value of A and the value of B are determined not by the proportion of A in B or of B in A, but by a third thing in which A and B are identical. But if there is no equivalent, there can also be no excess over the equivalent.” (p 209)
But, Ganilh faces a contradiction here, because for him, there is no equivalent. The actual basis for the exchange relation of A to B is that both are the equivalent of some third thing, which is their value, i.e. the labour-time required for their production. However, for Ganilh, the exchange value is nothing more than the actual proportion in which they do exchange. But, then on this basis, there can never be any excess over the equivalent.
Suppose 10 tons of iron exchanges for 1 kg. of gold. By the same token,, after the exchange, I have 1 kg of gold rather than 10 tons of iron. If I exchange the gold, I can similarly only obtain 10 tons of iron. There is no basis for any excess to exist here. Whatever the exchange relation in one direction, it applies equally in reverse, in the opposite direction.
“If therefore I gain on the original transaction because less gold is equal to more iron, I now lose just as much because more iron is equal to less gold.” (p 209)
There are only three ways that an excess can exist. Firstly, if 10 tons of iron is equal to 100 hours of labour, and 1000 metres of linen is equal to 100 hours of labour, then if I sell 10 tons of iron to B, but only buy 500 metres of linen from B, then B will have to make up the difference in money, equal to a value of 50 hours of labour.
Secondly, if 10 tons of iron required 100 hours of labour for country A to produce, but 200 hours for country B to produce, whilst both produce 1,000 metres of linen in 100 hours, then B will have a reason to buy iron from A, at a price higher than 100 hours, but less than 200 hours of labour. In that case, A would expend 100 hours of labour, and obtain a greater quantity of labour in return.
Thirdly, there could be simple cheating. A may exchange 10 tons of iron for 1 kg of gold in Market X, and exchanges 1 kg of gold for 12 tons of iron in market Y.
In the first case, this is not really a surplus either. If the gold or silver paid as money to make up the balance is used to buy other commodities, then the same exchange relation exists. It was considered a surplus by the Mercantilists, because this money resulting from a trade surplus was seen as the basis of expanding domestic production, and thereby exporting even more.
The second case also does not produce a surplus of value in reality. Both A and B may enjoy an absolute or relative comparative advantage, as Ricardo demonstrates, as a consequence of specialisation, but for the reason Marx sets out above, the purpose of the exchange is for one side to obtain use value, and the other exchange value. Both sides obtain a greater quantity of use value for a given expenditure of labour-time. They experience an increase in what orthodox economics calls welfare.
But, if A then comes to sell the commodities, they obtained via the exchange, they can only sell them at the market rate, not at the cost of production for A. What A gained in buying at a lower cost of production, they would equally lose if they came to sell.
A surplus could arise from cheating, as described in the third case, i.e. from unequal exchange. That is the situation Marx described earlier in relation to James Steuart, and the concept of profit on alienation. Taken as a whole, what is a gain for one is a loss for another. However, its obvious why for the Mercantilists, operating in a time of colonialism, this idea had obvious attractions, because it appeared that a process whereby maritime powers such as Britain and Holland, could simply continue to amass wealth on the basis of such continued expansion of trade on this unequal basis.