  It is a well-known fact that the non-pluripolar self-products of a closed
positive (1,1)-current in a big nef cohomology class on a compact Kahler
manifold are not of full mass in the presence of positive Lelong numbers of the
current in consideration. In this paper, we give a quantitative version of the
last property. Our proof involves a generalization of Demailly's comparison of
Lelong numbers to the setting of density currents, a reversed
Alexandrov-Fenchel inequality, and the notion of relative non-pluripolar
products.
