I agree with removing the +buy. I would also suggest adding a minimum bid of the cost in coins of the card revealed. I'd like to see what happens when one person bids highly on a card to keep another player from, e.g. improving his engine, and how much it warps his/her strategy after the fact. I do not agree, however, that it would be bought very often. There is way too much variability in what type of card you are bidding on. Maybe do like the original Black Market, and have the person who played the card choose one of three. Lastly, you need the setup clause adding the black market deck. If black market isn't in the kingdom, there is no black market deck to reveal cards from.