That sounds about right, 2". I own a couple of pairs of boots. I'd say they add anywhere from about an one 1/2" to 3 1/2" depending upon how their made and how high the heel comes up and how much padding is on the inside.
They're just like any boot. They make you as much taller as the bottom and soul of the boot are thick. If the bottoms 1" thick than you're 1" taller give or take your weight and how much the bottom/soul squishes.