I am not sure that this is quite optimal, but I get $4800.

Village, Smithy, King's Court, Hermit (thus Madman), Vault, Coppersmith, Bank, Contraband, Fool's Gold, Counterfeit, Philosopher's Stone (thus Potion). At the start of your turn, you have all ten Coppersmiths and Banks in your deck, you have one Hermit and eight have been been trashed, you have eight Madmen (you can't get nine and still have a Hermit), and you have all but one of every other card.

You have a Madman in hand to draw up to 12 cards, including two King's Courts, two Madman, and a Hermit. KC/KC/KC/Madman/Hermit/Madman draws you from 8 cards up to 16, 32, and then 64. Use the Hermit to gain the last Copper, Fool's Gold, and Village. The second KC'ed Madman gets you up to 492 cards, which is more than there are in play. You have 13 actions and your hand is now:

9 Villages, 8 Smithies, 7 KCs, 6 Madmen, 9 Vaults, 10 Coppersmiths, 10 Banks, 9 Contrabands, 10 Fools' Golds, 9 Counterfeits, 9 Philosopher's Stones, 9 Potions, 60 Coppers, 39 Silvers, 29 Golds, 9 Platinums, 10 Estates, 7 Duchies, 7 Provinces, 7 Colonies: total 263 cards

The 7 KC's will allow you to triple 13 actions. You need to triple all 10 Coppersmiths, and you can't play any un-tripled actions in the middle, so you want to Vault/Madman/Vault before tripling, then use a tripled Madman/Vault/Madman/10x Coppersmith, then Vault at the end to discard all the unused actions. The tripled Madman multiplies your cards by 8, and you will need 252 cards at that time, so you want to have 32 cards left. Thus you play the first Vault discarding 131 cards down to 131 ($131), Madman drawing back up to 261 cards, Vault discarding 221 cards down to 40 ($221), 7xKC, tripled Madman drawing back up to 252, tripled Vault discarding 218 cards down to 33 ($218), tripled Madman drawing back up to 250, tripled 10xCoppersmith, Vault discarding 9xVillage, 8xSmithy, 3xMadman, 5xVault, 10xEstate, 7xDuchy, 7xProvince, 7xColony ($56). Copper is now worth $31, and Philosopher's Stone is worth $11. Counterfeit the Coppers so that you have 69 Coppers (but the counterfeited Coppers are no longer in play and do not count for Bank)

69 Copper are worth $31 each for a total of $2039. The Silvers are worth $80, the Golds are worth $87, the Platinums are worth $45, the Contrabands are worth $27, the Fool's Golds are worth $37, the Potions are worth $0, the Philospher's Stones are worth $55, the Counterfeits are worth $9, and you have 174 Treasures in play (9 Coppers have been trashed), so the Banks are worth $175-184, and $626 from the Vaults.