Items with infinite usage
None of the other items actually reduced cost. For the latest item you are looking at multiple decades. Depending on the player’s current age and play pattern they might not even live long enough to break even on the cost.
So if they follow the same pattern there be a WP item that will increased the cost of WP for some sort of convenience. Maybe let you access any WP as long as you’ve unlocked it on at least one other character or you act as a WP for your party and you pull them to your current location.
reducing wp costs would not be a convenience item. you don’t need to bring teleport guns around with you to wp. they already are in the convenient form – unlimited and consume your gold, exactly like the unlimited salvage kit.
I could see mounts being added to the gem store. those at least have a convenience over the current system of running.
Mystic’s Gold Profiting Guide
Forge & more JSON recipes