As a rough indication, and I'm only talking the computer industry in relation to one big player (him) and one very small player compared to him (me). HN buy alot (not all) of their computer gear from the same suppliers I do, yet because of volume they obviously buy a hell of a lot cheaper than I do, but going by my buy price and his sell price there is no way he's adding 80%, if he is they are giving him the stuff.
They make their money purely because a large number of idiots believe their mass media campaigns. Buyers don't take into account that cheaper parts are used, they don't take into account that a warranty will take 8 weeks to repair, they don't take into account that the staff don't know a USB port from a VGA port, they just go there because the ads say they are cheaper. To be fair this isn't just a Gerry issue, DSE, Myer, Tandy and the like are all the same when it comes to selling this crap, limited real knowledge but convincing sales pitches.
I know this doesn't just happen in the PC industry it happens where ever big business wants to stomp on little business, and I'm not bitter because I've made a lot of money fixing computers people brought at HN or the like but refused to take back because they get no help. But it's like one interviewer said to Gerry, business like his stopped supporting Australia when they went off shore for labour and products but now they want us to support them when they are getting played with. Big Business has had it their way for so long they think they have the power to push people around and make us feel sorry for them.
On the note of profit margins I have never tried to compete with the prices of Gerry and Co but I have also never worked on 80% profit because the market just can't support it, however an ex-client of mine who operates in the retail sector has been told by her suppliers on many occasions that 85% in the minimum markup she should be looking for and in most cases she gets it, so different sectors do allow for large profits.