Thank you GeorgeB for the clarification and the reinforcement of the BB explanation as literal truth. As I stated early on, if the BB explanation was the truth, I would owe Tesla a big apology. And so I do, and will offer it here: Tesla and GeorgeB, I am truly sorry for not taking your explanation at face value, and then publicly accusing you of falsely representing your motivation and pricing in order to justify a future price increase (which, BTW, is still completely justified when it does occur, as far as I am concerned).
I was being far too cynical. After so many years of dealing with Acura, BMW and Porsche, where the thought of those companies configuring a costly bonus option into a high-end configuration at no additional price increase to the customer is not jut unlikely but downright laughable, I simply could not accept what appeared "too good to be true". As I myself stated even before GeorgeB's post above, I need to be more like the Roadster owners who have learned this repeatedly in the past: "If it sounds too good to be true, it must be Tesla."
And to all who piped in with the argument for the Performance being a bargain, you were also right and I was wrong, to say there was no relation between the two issues. This explanation makes it clear that the Perf is even more of a bargain than we all originally thought, as now we know it includes free 21" wheels...making the two issues very much intertwined.
I only wish this had been explained earlier, perhaps on the multiple phone calls and Emails I sent to various Tesla representatives at Ownership experience since early Summer, as it might well have encouraged me to configure the Performance upgrade, rather than acting as a discouraging factor against it. Instead I was only told that it had been discussed and decided that no credit for the 19" downgrade would be offered. Wouldn't the truth in this case have been a much better sales opportunity for Tesla?
Anyway, enough from me once again. I apologize for my insinuations and accusations, and I am thankful that my tirade has not discouraged GeorgeB and the Bulletin Board concept overall.
I still think storing and switching tires is a royal pain, in practice not just in theory, and this is further complicated by the requirement of a TPMS reset by Tesla Service center (or Ranger?), which are all more than 300 miles from me currently. Having said that, if Tesla offers OEM 19" turbine style wheels in 2013 or beyond, they will become my summer wheels in a heartbeat!