Bob, FWIW, I can testify that the Factor, which is advertised as a 130 flex, and talked about as at the burly end of the AT spectrum, is more like a 100 flex Salomon. I can bracket it because when I owned the Factor, I was also skiing a Sollie plug (130 and I think that's about accurate), and a Sollie Falcon 10 (110, ditto), and a Sollie 9 (90 flex). A few times I skied a couple on the same day, same conditions, same runs, just cuz I was curious. Maybe the Factor was aberrant, but the feeling over at TGR, which has an entire thread on this issue, is that AT flexes are exaggerated.
Second, while most folks have been known to be wrong, it's more typical that most folks are right. In this case, obviously the issue is: "X works fine for me on Y conditions." Setting aside how a psychologist would view reducing our cognitive dissonance over stuff we own and ski, how do we know that "works fine" for you is the same as "works fine" for me? Chris uses Alpine Trekkers, which serious backcountry types wouldn't be caught dead on, and they work fine for him. I've read posts from guys who use 130-150 flex alpines, or in one case, plugs, for skinning. All meaning what?
Third, AT is a small niche within a small sport called skiing. I'd suspect that AT boots have a higher relative cost to make and lower profit margin, largely because their unit sales are so much lower - so takes longer to recover cost of molds etc. - and they have more moving bits - or in the case of the unlamented Quest, non-moving bits - that can go wrong. So manufacturers would have more incentive to market them as the second coming and sell more in order to recover costs. But manufacturers don't. Because they're not.
Fourth, tromano is right. The soles make a big difference in terms of release reliability and rigidity to transmit force from leg to ski edge. Several threads at TGR on release issues, and Lou at Wildwood has done some stuff too. Rigidity is pretty obvious, why plugs are so freakin' thick.