In
Sid Meier's Alpha Centauri (
SMAC), the Merchant Exchange is a
Secret Project. It may be built at a cost of 180 minerals, on discovery of
Industrial Base (B1). The Merchant Exchange increases energy production by 1 in every square of the production radius of the base where it's built.
How useful is this? Since its effects apply only to the base where it's built, I can't call the Merchant Exchange a "good buy". At best, it will provide an additional 21 energy per turn, but early to mid-game conditions will limit it to around 7-10 energy per turn.
As a game interpretation of existing financial hubs like Manhattan's Wall Street, the Merchant Exchange is one of the least sci-fi-ish Projects in the game.
Secret Project animation narrative:
"Human behavior is economic behavior. The particulars may vary, but competition for limited resources remains a constant. Need as well as greed have followed us to the stars, and the rewards of wealth still await those wise enough to recognize this deep thrumming of our common pulse."
-- CEO Nwabudike Morgan,
"The Centauri Monopoly"