I, personally, understand the reason (other than greed) why this extra tab doesn't apply to all characters.
There's a huge difference between in gain between a 4 character account and a 10+ character one.
What I do not understand is the pricing. If I really am in need of some extra bank space, it's cheaper just
to buy another character slot. Additionally you get MORE storage space this way (inventory + bank slots).
If you have a shared bank and a veteran status item transfer is a breeze.
Price that extra tab at 245-295 TP per character and it might sell for convenience factor alone.
I don't like the idea of store-exclusive items myself, but I think that the extra bank tab is just a convenience
feature and not a necessity, therefore it doesn't have to be achievable in-game "for free."