Hmmm....does this work? You need to play black market....60 times I think, since you can only buy one card per BM play. So, money is not the issue here (unless I'm misunderstanding your proposal)
Oh, I thought 15 cards. Then, how about Overlord-Crown method?
Fewer cards I have found to loop infinitely.
6 cards, no Event
Kingdom: Overlord, Lurker, Raze, Watchtower, Crown, Mandarin
Setup: trash Mandarin
Deck: 5 Overlord, 2 Watchtower
You have 2 Overlord and Watchtower in your hand.
play Overlord as Crown
-- play Overload as Crown
---- play Watchtower
---- play Watchtower
-- play Overload as Crown
---- play Overload as Crown
------ play Overload as Crown
-------- play Overlord as Raze (trash itself)
-------- play Overlord as Lurker (gain Mandarin, reveal Watchtower to trash)
------ play Overload as Lurker (gain Overlord)
---- play Overload as Watchtower
Now you have 5 Overlord and Watchtower in your hand.
LOOP FROM HERE
play Overlord as Crown
-- play Overload as Crown
---- play Overload as Crown
------ play Overload as Crown
-------- play Overlord as Raze (trash itself)
-------- play Overlord as Lurker (gain Mandarin, reveal Watchtower to trash)
------ play Overload as Lurker (gain Overlord)
---- play Overload as an Action costing up to $5
-- play Overload as Watchtower
LOOP END
Use Band of Misfits and Ferry instead of Overlord to make this more practical.
Replace Pooka to Black Market, whose Deck has Pooka, Watchtower, Young Witch(, whose Bane is Lurker), Mandarin. Add Crown. After you've got enormous Treasures, 2 Black Market, Library in hand, play those Black Markets to gain Watchtower, Mandarin (reveal Watchtower to trash). Use Pixie instead of Raze.