That was before FICO :-)
Anyway, you can see quickly how that can't possibly be true; it would have to be how much _mortgage_ you can afford. A $30k income can "afford a $12M house" if they have an $11.9M downpayment ...
But yes: housing costs are expensive, whether you own or rent. Unless you have been living in the same rent-controlled apartment for the last 15 years :-)
(Just imagine if you shopped at a grocery-bill-controlled store!)
I think the problem with looking at percentages is that it doesn't scale. What someone with a $50k income can afford is not half what someone with a $100k income can afford: if you make more, you're often more willing to devote a larger percentage of your budget to housing, since getting twice as much house doesn't (typically) mean you pay twice as much for gas.
I think it's a lot more useful to try to figure actual [net-of-tax] monthly costs when comparing own/rent scenarios.
/jordan