When expandating, we can carry more item!
Add 50 slot for the inventory after each expandation!
Cost: Gold (10000 for the 1st, 15000 for the 2nd, and so on)
and Plat (5 for the 1st, 10 for the 2nd, etc...)
(Plat only is also fine to me)
Say ":D me" if this has already been suggested
Or you could make it 1k for every extra 25 items you can add to your inventory or something like that. 10k is a bit much but plat only makes even more sence