Marx was not an economist. As Korsch noted, he did a reconnaissance mission over the terrain of political economy which always remained enemy territory.
Those who have appreciated Marx's magnum opus as a destruction of economics (a discourse which simply takes over, systematizes and transhistorices all the irrational expressions of common sense--the value of a debt, the price of capital, the trinity formula, the value of labor and other yellow logarithms) include
Karl Korsch (Karl Marx, 1938), Derek Sayer (Marx's Method), Jacques Ranciere's missing contribution to the English version of *Reading Capital* (though trans in Ali Rattansi, Ideology, Method and Marx), Paul Mattick (Marxism: last refuge of the bourgeoisie?), Cyril Smith (Marx at the Millenium), Robt Paul Wolff (Moneybags Must be so Lucky), H G Backhaus's contribution to Open Marxism, vol I, ed. Werner Bonefeld; Paul Mattick Jr ('Theory as Critique' in Fred Moseley and Martha Campbell, eds. New Investigations in Marx's Method)
Bukharin thought of Marx's theory of value as doing better than Austrian ones in explaining the dynamics of 'price'--the domain of economics. Bukharin was wrong, but I need to think about this and reassimilate all that reading I once did again.
The erudite Drewk could jump in here of course.