The 'Golden Triangle' of Theatre Production (or Scenic Construction, etc), is a golden rule of concept and a good "rule of thumb".
Imagine a Triangle with three sides: Good, Cheap or Fast (Quality, Price, Speed)
You can emphasize one or two of the sides of the triangle, but only by taking away from the others. If you want it good and cheap, the less fast. If you want it Fast, it may not be good or cheap. Pick one, or two. You can never have all three.
There are also other 'Golden Triangles' one could make, as they are a good indication in concept of the thought process to help realize the truth of a situation.
(examples of other Golden Triangles?)