> Perhaps. But, nonetheless, isn't it the case that all the
> significant theorizing about monopoly and oligopoly pricing
> (even Sweezy's "kinked demand curve") has taken place on
> an entirely Marshallian basis?
I'm not sure I understand what you mean here. Marx was trying to get his critique of political economy published in the 1850s-1860s. On political economy (as opposed to, say, blasting the anarchists), his output in the 1870s and early 1880s was very modest by his own standards. Marx's attempts in the mid and late 1870s to organize his drafts for publication (as volumes 2 and 3 of Capital), mostly "collecting" the material rather than "sifting" through it, led him to depression -- says Engels in the preface to volume 2 of Capital. He died in 1883. Most of the stuff Engels, Kautksy, and others later compiled and published dates back to the 1850s and 1860s. The first volume of Marshall's Principles were published in 1890. He became most prominent and influential in the 20th century. So I don't see why one can reproach Marx for not having engaged Marshall's partial equilibrium stuff.
> And where is Marx's theory of secular change (inflation/deflation)
> in the price level? Isn't it rather the case that Marx's deep
> interest was not in prices at all, but rather in the laws of motion of
> the capitalist mode of production and most especially in the "Law
> of the Falling Tendency of the Rate of Profit" and its effects?"
I think that counter-posing the FROP to prices is misleading. It's like counter-posing anatomy to physiology. Marx's FROP is built on an understanding of value and its price forms. The notions of value and price are the framework for the whole FROP discussion.