A Tech Pyramid, or Technology Pyramid, is an assembly of Research Complex and Hi-Tech Goods Factories built at a ratio of 3:1 or higher. The reason this is done is because a research complex raises the Hi-Tech Goods price on a planet at roughly one third the rate that a Hi-Tech Factory will decrease the price. This means that a much, much larger number of Technology facilities can be sustainable built on a planet than any other sphere (except maybe Mercantile Pyramids).
Tech Pyramids are considered a Game Exploit by some, since their functionality does not mimic real-life markets. When Tech Pyramids were first discovered and implemented, it was possible to use a good administrator and a high tech level to build enough facilities to cap the price of Hi-Tech Goods at 160 solars. Since research complexes only require 40 solars a piece to maintain at that price level, it was possible to maintain 3 research facilities per hi-tech factory and still maintain hefty profits. Some planets that houses tech pyramids could host several thousand facilities.
The role of tech pyramids has changed since the implementation of several influence and sphere-leader adjustments that make profitable tech pyramids more difficult to achieve. Pyramids are still used, however, to sustain large scale research, since a 3:1 ratio is the most sustainable way to build large numbers of research facilities. As Tech Level is such an important statistic in the game, the costs to keep negative income Tech Pyramids running is often worth the cost.
A Merc Pyramid, or Mercantile Pyramid, is an assembly of trading hubs on 2 planets, where the same good is exported and imported. Normally, the profit from each route cancel each other out, but good Administrators would increase the profit made on the positive route, and decrease the loss on the negative route, making each import/export pair profitable. Optimized Merc Pyramids kept one planet with the minimum price for the chosen good, and the other planet with the maximum price. Precious Metals was usually touted as the 'optimum' choice for trading due to its highest price difference of 12-240 at minimum and maximum, though Objets d'Art was quite profitable as well with 10-200. These pyramids would boast several hundred hubs each, and profits from these pyramids became so large that the GM implemented the Sphere Leader Nerf specifically with the intention to prevent mercantile pyramids from being feasible at the scale they were being abused.