Similar question whose answer is probably a combination of the all the answers to the last question... what is the most number of cards you can gain from a single buy?
let's see... 4 player game, play 10 hagglers, 9 talismans, buy a doctor (gain the other 9) with 30 embargoes on it, gaining 10 of a 2 cost. Overpay by 22, discard 12 tunnels, trash 10 catacombs, gaining 10 death carts and 20 ruins, discard 10 market squares.
kingdom: haggler, talisman, doctor, black market, tunnel, catacombs, death cart, two-cost, market square.
black market deck: young witch, embargo, graverobber, bunch of cards to let you draw and play all that.
+10 doctors, +30 curses, + 10 two-costs, +12 gold, -10 catacombs, +10 death carts, +20 ruins, +10 gold.
net +92 cards.probably improvable... for instance, trashing cultist to draw 3 market squares?