This just causes confusion as to whether you have it permanently or not. A system like how diamonds work on the island would probably be easier to understandFor example, it could be two opinions, 10 gold for a key you need to carry and hold in hand to open it and second 10 diamonds, which you only need one time to click it and it will be unlocked for the rest of game after you unlock with that key you don't need to have anything to open it, you can open it with emty inventory.