I've written before about my respect for Marx the man, but his alleged followers a bunch of dingbats. They can't even interpret his theories correctly, they present these second-hand notions from long-dead communists who came after Marx as if they hadn't been completely discredited even in the eyes of socialist economists about fifty years ago (yes, there are still socialist economists out there, but they're mostly ignored given how wrong they have been). It's like going to the library, checking out some eighty-year-old book on reading head bumps to predict peoples' futures, and then explaining how this head bump thing "totally debunks" modern psychiatry, psychology, physiology, etc.
Thus production price determines the price of a commodity, not supply and demand, in the long term. In fact, price determines demand as consumers face prices as (usually) an already given objective value when they shop and make decisions based on these prices. The production price for a commodity is a given and so only profit levels indicate whether a given product is “valued” enough by consumers to warrant increased production. This means that “capital moves from relatively stagnating into rapidly developing industries... The extra profit, in excess of the average profit, won at a given price level disappears again, however, with the influx of capital from profit-poor into profit-rich industries” so increasing supply and reducing prices, and so profits. [Paul Mattick, Economic Crisis and Crisis Theory, p.49]
I've quoted this paragraph because it's the crux of his argument, and anybody familiar with economic history will read this paragraph and go "mm hmm, mm hmm, and for a while in the 1800s this appeared to be true to some people but it was quickly discredited by Marshall, and then further buried by the socialist Oskar Lange" or mental words to that effect. It really is like a time capsule for one school of thought from another time, but of course the the flaw in the crux of that paragraph, the crux of the crux, is that production prices are not a given but float with supply and demand just like consumer goods prices do.
Marx had a theory (which this guy presents a bastardized version of) which turned out to be false. Prices do not work the way Marx thought they did, as we now know with total clarity. And the whole surplus profit idea was dropped completely. You don't have to be Milton Friedman to see that Marx, brilliant mind though he was, was just wrong because his "givens" were wrong. So his whole analysis fell apart, I mean it was falling apart before it was even fully published.
But one thing that irks me about pseudo-Marxists is that they don't seem to care about what happened in the 130 or so years since Marx died, or in the 100 years since Lenin distorted the heck out of Marx's writings and gave us what people think is Marxism. They whip out these discredited analyses and archaic definitions and if modern economics conflicts with them, then they say modern economics is wrong. Which is like saying that a body of knowledge, of empirical data and a better understanding of the cause-and-effect relationships and "laws" that govern any economy (socialist, capitalist, fascist, etc.), that took over two hundred years to build is wrong. Just because of what they read about in Philosophy 101.