I've heard Rollo on youtube and also noticed the voice narrator of his audio book The Rational Male mispronounce the word. They seem to say hyper-gammy for the pronunciation. Yes I know t doesn't really matter but it's slightly annoying while trying to listen to the book. Is it a regional thing or a reason he says it that way?

This is the correct IPA pronunciation: /hīˈpərɡəmē/