Mage Cap building to Rabadon's

Making a cheaper and weaker version of deathcap like:

Mage's Cap(1785 gold):

60 ap Unique passive: +20% ap Note: rabadon's is +35% ap

Needleless Rod + Mage's Cap + 765 gold = Rabadon's Death Cap

Needleless = 60 ap Mage's Cap = 60 ap Rabadon's Death Cap = 120 ap (numbers add up well)

Blasting Wand + Amplifying Totem + 500 gold = Mage's Cap Blasting Wand = 40 ap (850 gold) Amplifying Totem = 20 ap (435 gold) Mage's Cap = 60 ap (numbers also add up)

This item will make the ridiculous build path of rabadons feel somewhat worth building for. You will be paying 500 gold for the unique passive alone. What do you guys think?