The index, a tool created by the Center for Neighborhood Technology, gauges the true cost of living in a particular places by factoring in transportation costs along with the cost of housing itself. Traditionally, housing has been considered affordable if it costs 30 percent or less of a household's income. In contrast, this housing and transportation index defines affordability to mean combined transportation and housing costs should consume no more than 45 percent of household income. By this measure--if I'm interpreting things correctly--most of Athens-Clarke Co. is not in the affordable range.
Here's the link for the Athens region. In addition to looking at combined housing and transportation costs, you can separate them out and also explore gas costs and greenhouse impacts by region. It's not the most intuitive site, but it's definitely worth a look.
(Via Discovering Urbanism)