You are not taking into account changing bulbs which does get costly when you using dozens of them. It used to take me two days to totally swap out all the track lighting in my mom's store. This is one of the huge reasons for the invention of the Twin Arc MH bulbs.. changing 100's of MH's in a warehouse is costly. It's not just about bulb efficiency in other words
Not to mention you can get them for $10 is you look in the right places.