Also it would be super unfair to the players who had to play all this time with a smaller bank, certainly they would all quit server.
How can you be so certain :p
If old players did that, the server would have never grown :p
There was a time when we had to farm for a couple of weeks to just get Dragon gear :p There was a time when one of the main ways to get r8 mats were through guild trials :p There's so much more i can list, no one left the server just because it got made a little easier to acquire those stuff for newer players.
Increasing bank space will only make things a little easier for everyone. It won't break the market. It's not like people can't multi client and store their shit among multiple characters as is. People are already money-hungry, i mean who doesn't like money lol.