So the thing is, alot of different items in this game when you get an item from a specific profession, lets take for example you get a skin for "Light" armour. Since the skin on all 3 professions is excactly the same, the game grants you all 3 skins for each profession. In short you get Light, Medium and the Heavy skin.
Question now is, why isn't that the case with Invisible boots? They are exact the same look. You can't be serious, making people buy all 3 of them (or drop them haha)... We speak about close to 9.000 gold. I don't know how many normal player have that much money to spend for feet... My suggestion is, buy either of them, activate them for your account and have all 3 unlocked. Because 9.000 gold is just stupid. That is literally equal to 4 Legendary weapons and thats insane...