Very nice trick.
But the Venture is quite important here, or? Getting the HoP to $5 can be done with every Treasure-Kingdom, but having $8 in hand does needs another treasure for at least $2, which is
Venture, Bank, PhilStone, Stash, Royal Seal, Harem, IGG (play Gold,Silver,Copper,IGG(gain Copper), HoP (Mandarin), Copper), Platinum (even enough for Colony)