  We prove, that Hausel's formula for the number of rational points of a
Nakajima quiver variety over a finite field also holds in a suitable
localization of the Grothendieck ring of varieties. In order to generalize the
arithmetic harmonic analysis in his proof we use Grothendieck rings with
exponentials as introduced by Cluckers-Loeser and Hrushovski-Kazhdan.
