In the PMP world, you will often hear the term Triple Contraint: Scope, Cost and Time which describe the interconnected and antagonistic relationship between these three factors. Put greater emphesis on two of these factors and the burden is born out by the third. Put in layman's terms when planning a project you need to decide what is most important between cheap, fast and good. You can only pick two. The third will be inversely affected, unless you're project is trivial, like making a grilled cheese ......