Such an old thread, lol.
I just don't like Potion Market at all. For the cost of 5P, what a bleh card. Possession at 6P is (IMO) the "strongest" card in the game, and is extremely different than any other card in the game. Golem at 4P lets you dig through to not just find 2 actions, but play 2 actions. The problem with Potion Market, is it is seemingly a card you want early (so you can get lots of them and spam them). The problem is at 5P you realistically won't be able to get one till turn 7 or 8 if you're lucky, and play it first on what, turn 10? This is the same problem Possession has, but instead of the chance of getting to play your opponents deck... you get a Market. And if you happen to draw it with your potion, you draw 2 more cards and get $2 (which is nice).
I'd recommend a small change to make the card more worthwhile at the price point, ie:
Potion Market
Action-Attack
$5P
+1 Card
+1 Action
+$1
+1 Potion
+1 Buy
Each opponent places a card from their hand on their deck, or gains a curse, placing it on the deck.
You may discard a Potion. If you do, +1 Card, +1 Action, +$1
I'm not sure, just seems too un-gamechanging for the price.