Fairgrounds has become quite an interesting card with Dark Ages anyway (as have the other Cornucopia cards).
Without Black Market, you can now have:
5 Basic Treasures (incl Platinum and Potion)
4 Basic VP cards (incl Colonies)
1 Curse
3 Shelters
11 Kingdom cards (Tournament, YW + Bane, Looter, Hermit, Urchin, Spoil-getter, Knights and of course Fairgrounds)
5 Tournament Prizes
5 different Ruins
1 Madman
1 Mercenary
1 Spoils
10 different Knights
For a total of 47 different cards, making each Fairgrounds worth floor(47/5) * 2 = 18 VP
Without Dark Ages there would be just 26 unique cards possible, so DA on its own adds 21 extra unique cards.