It means exactly what was said in the part that you cut out:

Where this has been the policy (in Connecticut for instance) the prices of every article have fallen & the money consequently is in demand; but in other States you can scarce get a single thing for it, & yet it is with-held from the public by speculators, while everything that can be useful to the public is engrossed by this tribe of black gentry, who work more effectually against us than the enemys Arms. & are a hundd times more dangerous to our liberties & the great cause we are engaged in—my best respects attend Mrs Pendleton, & with much truth & regard I am Dr Sir Yr Obedt & Affe Servt

https://founders.archives.gov/documents/Washington/03-23-02-0113

Other part of the quote comes from a completely different letter:

It gives me very sincere pleasure to find that there is likely to be a coalition of the Whigs in your State (a few only excepted) and that the Assembly of it, are so well disposed to second your endeavors in bringing those murderers of our cause—the Monopolizers—forestallers—& Engrossers—to condign punishment. It is much to be lamented that each State, long ’ere this, has not hunted them down as the pests of Society, & the greatest enemies we have, to the happiness of America.

https://founders.archives.gov/documents/Washington/03-18-02-0452

What rank dishonesty.

They should have picked their own cotton.