A lot of the early ST adopters purchased the FoST as a third vehicle, a toy of sorts. Due to the entry-cost (back during markup days), most people didn't want to toss that kind of money on a daily-driver when you can either buy something substantially cheaper or better optioned. The majority of the overall population fall on either sides of that line. A surprisingly large amount of ST owners also, through my observation, just wanted a sporty daily because their 'fast' car was a significantly more 'worthy' car that they just didn't want to put miles on every single day at the expense of single-digit or low-teens in fuel economy. The FoST was a happy medium of performance and overall cost.
Now that the price-points of final sales have come down on the FoST I'm sure a larger percentage of lower earners have jumped into that bandwagon, but the overall community is still populated by many very, very 'smart' individuals-clearly people with degrees and/or larger amounts of life experience-it's very evident in online interactions. While that isn't exactly a prime deciding factor on how much an individual earns, you can draw lots of lines of similarity and make general assumptions. When I first read a Ford statement a couple of years ago citing basically the same information of household worth I initially viewed it as subtle marketing hype to draw in higher earners, but after spending time in the community I began to think and agree that it's possibly true. Most of the early BT adopters didn't care about their warranty or having their car down for any extended period of time because they had other cars to fall-back on and if they blew their motor they could just buy a new one.
But in all fairness, a really smart and highly schooled member can work at the local Wal Mart just as easily as someone with less schooling/book knowledge can rise to a decent income in a blue-collar position.