This is an interesting overview of things and helps highlight the solid work Zeroqode has done developing and marketing their products. But as a template developer (Top Shelf Templates) I can assure you that the numbers are much smaller, which I think Levon could attest to as well.
A couple of reasons why:
Many templates started out at a lower price or even as Free in order to ‘boost’ the install numbers. Since the number of installs is (or at least was at one point) is how templates get sorted in the marketplace, there is an advantage to have templates that have a high number of installs as your templates get seen first
Discounts & freebies - coupon codes can be offered for the templates, as well as temporary price reductions making the numbers lower