Again, there is no valid BUSINESS reason to do so.
You didn't let anyone know about the added value, yet boosted the price because of the added value? No, that only works if you advertise the item as being more-than-average ie premium. The item was inflated in price without telling the player base why.
I think you misse the point... NONE of the Bags were supposed to be BtA. They are ALL meant to be BtC. Even a small BtA bag breaks things.
In this particular instance I'm going to assume the worst, not the best, because it was not done transparently. Had you made an announcement that "Huge Bags have inflated in price because they are currently more valuable than anticipated," everyone would have ho-hummed and thought about it. Even a "Temporary Value Increase" post would have clued players in without stating, "Yeah we're going to remove that bind-to-account feature." Hiding all of the operations behind the bag's situation was not transparent.
I also conclude that most VIPs will not be purchasing your Huge bags anymore as we can do better with Medium/Large Bags that can be shared.
PS: Please don't make those bind -- it would only make the Huge Bag issue an absolute deception.