"Tyler Cowen (/ˈkaʊən/; born January 21, 1962) is an American economist, columnist and blogger. He is a professor at George Mason University, where he holds the Holbert L. Harris chair in the economics department.[2] He hosts the economics blog Marginal Revolution, together with co-author Alex Tabarrok. Cowen and Tabarrok also maintain the website Marginal Revolution University, a venture in online education."

I think it is pretty safe to assume that at the very least in this case Graeber was correct.