Organization don't conduct projects for laughs.  Every project has to deliver value to the organization. Planning for which project to undertake begins months before any project is authorized.  Many factors go into the project selection but one of the most important is the calculation of the Return on Investment (ROI)  This is also known as the Benefit to Cost Ratio.  Most organization have a standard gate that is used to help in the selection process.  A ration of 5:1 is common.  Once the project is selected this BCR is a primary input to the prioritizing of the many projects being considered.  If the ratio falls below the selection gate the project may require reconsideration.