I can get 253 (edit), which I'm sure can be optimized significantly.

Kingdom: (Note: I'm intentionally not using Nocturne cards)

Fool's Gold (bane)

Black Market

Cache

Capital

Charm

Contraband

Royal Seal

Treasure Trove

Harem

Hoard

Bank

BM Deck contains (at minimum): Hermit, Lurker, Young Witch, Poor House, Fortune, Philosopher's Stone, Bandit Camp, Tournament, Rocks, Plunder, Talisman, Ill-Gotten Gains, Humble Castle, Crown, Stash, Horn of Plenty, Coin of the Realm, Loan, Quarry, Venture, Counterfeit, Relic, Bazaar, Mining Village

Setup: Deck contains 10 Madmen, a Trusty Steed, a Diadem, a Poor House, 15 Spoils, 11 (edit) Platina, 10 Banks, 10 Capitals, and all but one card of every other kingdom pile. It's a 3-player game, so there are 12 Harems (of which you have 11). You also have one copy of every treasure in the Black Market. Assuming I counted correctly, this is 267 treasures. Additionally, you have a Bazaar and a Mining Village, and you still have a Bandit Camp. (You also probably have other cards in your deck, such as a Tournament, a Province, and the Lurker which you used to get the Hermit back a bunch of times and get more Madmen, but these cards don't matter.)

Start: You have 5 Madmen in hand and 5 on top of your deck

Play 8 Madmen to draw your deck. Play Bazaar, Mining Village (trashing it), and Bandit Camp. Play 9 Black Markets. On the ninth one, play Treasure Trove (gaining the last Copper and Gold), then 5 Capitals, then 8 Banks, then a Fortune, for a total of $258. Play Steed for coins and Silvers (gaining the last Silver). Play Madman to draw the new treasures. Play Poor House.

Your hand contains 253 treasures, assuming I counted correctly. Before you reveal your hand, you had $264. Afterward, you have $11, for a score of 253.