If you have more than 20 thousand BC in your treasury, make sure you rush build something, because you take a major economic hit when your treasury gets that high. For example, i did a test during early-mid game with the Terrans, under 20 thousand i was bringing it about 498 BC/turn. The next turn when i let my treasury stay over 20 thousand BC, it dropped to bringing in -178 BC/turn (No other changes were made to slider settings or anything to cause this difference). Thats a huge difference1!