If it was cost efficient for RuneScape gold them to maintain selling bank boosters they'd. Money is their goal, so we can probably infer that for the price the cost, selling more boosters would not reevaluate the drain of having more people using more stuff stored in the server. I'd love additional space, but it's unlikely that we will get anything any time soon. You can save 2 bank spaces though, only get the last soulstone, and then combine them into 1 thing.
It's actually supposed to be since they were hitting technical limitations in the amount of time it'd take to load/transfer/search banks of bigger sizes. We obtained the lender placeholders update instead although I believe that the bank rework was supposed to fix this. Storage on this scale is economical, we are talking about 2 bonds for 50 distances and regarding information an item is just a numerical item id, a numerical volume and a bit of metadata. I can not say for sure just how much metadata a thing can happen but even if they allowed for more metadata than I have ever seen evidence of in game and things could be 100 bytes each that would only be 5kb of storage.
Within our inflated example of 100 bytes each item, you can store 400 million things for $9.99 per month using dropbox. If individuals paid $6.99 a bond to fulfill that 2TB, then Jagex would make $111,840,000. It would take over 11 million years to buy OSRS gold the price of that hosting to reevaluate the profit of the 1 time bond sales and that is assuming that everyone purchasing the area is p2p because f2p cover 3 bonds instead of 2. Obviously it's a little more complicated than that but I hate when folks claim that Jagex can not handle storing additional data.