Some quick points:
(1) Although she finds some value in Marx, her condemnation of the labour theory of value is nevertheless fairly harsh: Robinson calls the labour theory of value a Marxist “incantation” and compares it to witchcraft (Robinson 1966: 22).In short, even one of the most influential founders of Post Keynesianism noted that contradiction between the theories of value in volume 1 and volume 3 of Capital, and the other problems and dogmas of Marxism.
(2) Robinson (1966: 10) notes the contradictions between volume 1 and volume 3 of Capital, just as Eugen von Böhm-Bawerk did in his much earlier critique of Marx (Böhm-Bawerk 1896 = Böhm-Bawerk 1949: 3–120). Of the two theories of value, Robinson preferred Marx’s exposition in volume 3 of Capital, which was a rather more intricate formulation than the “simple dogmatism” of volume 1 (Robinson 1966: 10).
(3) Robinson, like other commentators, noted that Marx needed to reduce all heterogeneous human labour to a meaningful homogenous unit (Robinson 1966: 12), but this actually “leaves open the problem of assessing labour of different degrees of skill in terms of a unit of ‘simple labour’” (Robinson 1966: 19). This is also exactly the point I have made too. There is a severe aggregation problem here that is never adequately explained by Marxists.
(4) If individual commodity prices were directly equal to labour value (and all labour were paid a wage rate commensurate to the socially-necessary labour time of each worker), then the aggregate output prices would equal the aggregate value of labour. But the problem is that there are different organic compositions of capital throughout the economy (Robinson 1966: 15). But, as Robinson notes, by volume 3 it is conceded by Marx that the rate of exploitation is different in different industries and relative prices do not correspond to values (Robinson 1966: 15). It follows, Robinson concludes, that Marx’s theory cannot provide any theory of price determination (Robinson 1966: 17).
(5) Robinson points out that, since machines can make labour more productive, Marx’s saying that only labour produces value is a silly verbal game (Robinson 1966: 18).
Böhm-Bawerk, Eugen von. 1949. “Karl Marx and the Close of His System,” in Paul. M. Sweezy (ed.), Karl Marx and the Close of His System and Böhm-Bawerk’s Criticism of Marx. August M. Kelley, New York. 3–120.
Robinson, Joan. 1966. An Essay on Marxian Economics (2nd edn.). Macmillan, London.