Just out of curiosity Andrew, why are you so avidly collecting Cycle and AB backed T205's if you don't feel that they are any scarcer or more valuable than Piedmonts?
One can always find individual data to try to prove a point and no doubt you have probably found some very good deals as you mentioned over the past several months. I think that most who actively collect the T205 set would place a premium on Cycle and AB backed cards. That's of course not to say that every such card will always sell for more than a similar card with a more common back. But overall, I am confident that this will hold true.
P.S. At your suggestion, I did a few minutes of research and checked recent sales on eBay. The last (and only recent) AB card to sell was this common:
http://cgi.ebay.com/1911-T205-Americ...item255639dba2
Note that none of the other SGC 70's of common players on eBay now even have an ASKING price of more than $275.