There is some discussion on this in another thread: Opening of the Day #1 (I believe).
In that thread, I was trying to assess the very same problem. I spotted a board where the only 2 viable strategies were Big Money plus Council Room, or Alchemists + Council Room/Money. I was surprised to see that Big Money handily beat Alchemists (as shown my Geronimo's simulator).
I was shocked to see this. I know that Alchemists are slow, but very powerful. I would have thought (first impression) that since the only other viable strategy was Big Money (which is typically the bounding-case slowest opponent), that Alchemists would win there. They didn't. So if they can't even beat the defacto slowest strategy, what the heck do they beat? And what tools were missing on that board that alchemists need (which at the same time, doesn't help big money by just as much).
I postulated that trashing was the missing ingredient, but I was countered by some of the top players on isotropic who mentioned that the trashing would likely benefit Big Money greater. This surprised me, but I would concede that their opinion certainly trumps mine.
So what is the missing ingredient then? Best I can see is the missing ingredient was Colonies.
If I have time I can play some more solitaire games, or mess around with the simulator more... but I'm having a hard time justifying EVER going Alchemists on a province board. Big Money seems to be strictly superior.
In terms of Colony Games, I would think the presence of trashing plus filter would help alchemists over big money. For example, something like Vault would certainly help the alchemist deck more than the big money deck.
/edit....
For anyone feeling adventurous (I would but I have no time atm), I'd be curious to see what the simulator says for a province game of:
Chapel
Alchemist
Vault
Council Room, Then as options for greater analysis of what the lichpin is, cards such as:
Steward
Bridge
Warehouse
Worker's Villiage
could help analyse under which cercumstances (i.e. support cards) alchemist strategies beat big money on province boards.
For example, I would be surprised if a deck like
Steward/Silver, then Potion, then Alchemists, then Treasure and a +buy card, finishing with a vault when you start to green up.
I think a deck like that should be able to beat big money + council room, even on a province board.
I'd love to see some simulator analysis done on that board.