Neoclassicals would say that in a general equilibrium model, price equals
payments to factor shares. (The rate of profit is thus zero) They would say
that it is arbitrary to point out that other factors are paid in addition
to labour. They could easily cite the claims (which can be translated from
neo-ricardian models in which they were formulated) made by Wolff (a
philosopher) but also Brody (an economist) that steel, wheat, etc are just
as exploited as labour. That is, Morishima's fundamental theorm can be
extended to show that the rate of profit is positive iff the corn, steel,
etc rate of "exploitation" is positive. (The translation would be that
other factors can be paid a positive amount if and only if the price of the
good exceeds the price paid for the selected factor (labour, steel, corn,
etc)