I love this game and I believe that the value for money is one of the best. You really get a ton of gameplay for what you paid for. Been playing since headstart and I am very satisfied.
But I am not gonna lie, this issue is one of the few things (lootboxes, infinite gathering tools [before they became acount bound] and most recent build templates being the other ones) that rubbed me the wrong way even way back then when I purchased my first (and after realising that it was character bound, my only) bag slot.
I am the type of person that likes to steadily upgrade their account so I choose to buy that kind of staff. Bank tabs, storage expansions, home nodes etc. But I will never be able to justify character specific unlocks for gems. It comes across as greedy and agressive.
I know that the goal of any company is to make money but there are many ways to go about doing that, some more customer friendly than others.