First of all, I think it is a great and bold idea to introduce a card with an auction mechanism into the game.
Second, one problem I see is that while the card increases the total number of Coin tokens held by all players and thus functions as a Coin token gainer it doesn't kickstart itself, i.e. without another card that provides Coin tokens it is dead. So perhaps you might wanna add the setup modification of Baker to it such that every player does at least have one Coin token.
Third, the other problem I see is that, unless there are other Coin token gaining cards, the scale for the auction is not fine enough: at least in the beginning 1 token will often suffice to win the auction and even later in the game players will probably not have a lot of Coin tokens available.
With 4 players Black Market Auction might suffice though as a Coin token "amplifier". Suppose everybody has a Coin token after setup, then 1 is spent and 3 are distributed so we have a total of 6. Suppose next time the card is played somebody spends 2 and 6 are distributed and now we have a total of 10 and so on.