Well Dave, I have gone back and looked through initial discussions for Light Sport aircraft and "affordable" was rarely if ever directly mentioned in notes from those meetings. The primary goal of LSA was to attract new entrants with reduced pilot training/certification requirements and new technology ready-to-fly aircraft. For the latter, it was thought reducing certification obstacles would generate an influx of new aircraft. It can certainly be implied that cost was a factor because there was concern the price tag on a new Piper or Cessna ($160K at that time) was a barrier for growing a new generation of pilots. ASTM F37 was created to make a set of compliance rules for light sport aircraft and again there is nothing about "affordable" published there.
Fast forward a few yrs and we have $150-$175 airplane style LSA's rolling off the assembly lines. Or $60k-$75k trikes that to me looked like a $5k ultralight with 2 seats. So yea, I too was stricken by the subjective "affordable" term and somewhat flummoxed as to how this was going to be an "affordable" activity. However, it appears to be clicking along. For a new aviation related industry I don't think it has done too bad. Compared to other recreational activity industries it would be graded a total failure but this is aviation. Different grading standards apply.