Don't forget tax etc.
Although I get paid £9.26 or so an hour in the UK. I only see about £5.00 of that as the rest goes in Tax and National Insurance. So while a £40 game (inc VAT) would be about 4 hours work before tax, it'd actually be more like 8 hours work after deductions.
You've also got the factor of, people will often buy more games for a single system, than save that money towards a much more expensive additional system, or spend that money on other things (night's out, DVD/Blu-rays, music or whatever).
It was a VERY ROUGH estimation for a "worst case" scenario: ALL consoles, ALL games (one/month). Still it is within reach for almost everyone with a full time work in the USA and most parts of Europe, especially if you consider yourself a video game hobbyist.