Basically I think a socialist society should not and will not value labour in terms of its exchange value, that's right. It stands to reason that if goods and services are produced for use value then labour cannot continue to be primarily an exchange value. Though none of that is quite the point.
In so far as we must, for present purposes, understand it that way under capitalism, there is a perfectly good reason that labour apparently has a different exchange value for different people, while still being of equal value in the abstract.
(This creates all sorts of misunderstandings. I have seen some people argue that skilled workers are part of the capitalist class because their skills amount to a form of capital and hence they are actually deriving their income from capital. Sort of right, except of course that skilled workers can't usually sell their skills without actually selling their labour too, so that isn't quite the same as a piece of machinery.)
Bill Bartlett Bracknell Tas