Thanks to luser I can now get 422 Silvers with 0 actions:
Kingdom:
Black Market (contained Venture, Watchtower, Quarry and contains Young Witch)
Counterfeit (empty)
Tunnel
Doctor
Cultist
Feodum
Hunting Grounds
Contraband
Talisman (empty)
Horn of Plenty
Catacombs
Hand: Watchtower, Horn of Plenty, Counterfeit, Counterfeit and Quarry.
Play Quarry.
Counterfeit chain:
Play Counterfeit.
Do this 4 times:
Play Counterfeit.
Play Horn of Plenty, gain Cultist, trash with Watchtower, draw Counterfeit, Talisman and Contraband.
Play Horn of Plenty again, gain Cultist, trash with Watchtower, draw Counterfeit, Talisman and Horn of Plenty.
Play Counterfeit.
Play Horn of Plenty, gain Cultist, trash with Watchtower, draw Talisman, Contraband and Trader.
Play Horn of Plenty again, gain Cultist, trash with Watchtower, draw Talisman, Contraband and Venture.
Play 4 Counterfeits and 5 Contrabands.
End of Contraband chain.
Play Venture, discard 9 Tunnels, reveal Trader to get 9 Silvers, hit and play Contraband.
Play 10 Talismans.
Play Contraband.
Total: 65$ and 32 buys.
Buy Doctor, overpay by 36$ and trash 9 Feodums, 9 Hunting Grounds, 9 Catacombs (reshuffle) and discard 9 Tunnels. Apply Trader to the Estates and Golds to get Silvers instead. Total: 72 Silvers.
Buy 31 Curses, gain 10 copies for each Curse, apply Trader to all of them to get 31 * 11 = 341 Silvers.
Total: 422 Silvers.
Any ideas how to improve this?