It would be all kinds of awesome (even with the high price tag) if the 10 extra shared bank slots would stack - even if a hard limit was imposed (say, 50 or even better, 100).
Extra character slots stack, right?
Why not make the shared bank slots stack, too?
I know I can use the inventory and bank space on each character for storage (and I do), but there are some things I like to keep in shared bank permanently so all my characters have access to them when I'm playing my alts, like guest passes and potions. But when I want to transfer stuff to different characters (or when re-rolling), it takes 2-3 logins/outs to manage all the stuff in alt inventories.
I would totally spend some major points on stacking shared bank tabs...even with the new point cost increase and the ridiculously high cost of the extra shared bank slots.
Anyway, just my 4cp (adjusted for inflation).