The flaw in this entire article is that GPU prices are in constant flux... and also vary tremendously from nation to nation.... what holds true for Australia might be completely backwards in Canada or the US... or the UK and France...
What is better (and Techspot has already done) is benchmarks for each card with as many games as possible... then you grab the card that makes sense to you - you just need to do some elementary math before you buy (is $20 in savings worth a 10% performance hit, etc).
To sum up... since GPU prices will be different next week (I suspect some are ALREADY different than what was used to calculate these charts), this article doesn't really work...