To be honest, I wonder if TI just didn't decide to always set the lowest downgrade version to one versions lower, from now on, or if it isn't just automatic when they compile a new OS?
As for the calc prices, over a TI-Nspire CX was $194.99 before it got heavily discounted before its discontinuing ($149.99 was the lowest I saw). I doubt that this made parents very happy. Just besides that calc, there was a nice Casio PRIZM for $129.99 (still overpriced, tho), while both the 84+ and 84+SE are around $140-150. I bet that over here, if another company released a calc as great as the 84+ with every feature and teachers were willing to learn how to use it, they would start recommending that calc to students instead, because over here, people always want to pay as less as possible.
However, I think the fact there are so many games on the 83+ probably played a role, too.