That's the kind of question that the Open Philanthropy Project is trying to answer. For example, here Givewell co-director Holden Karnofsky a back-of-the-envelope calculation for DALYs created by life sciences research. Here is a similar back-of-the-envelope question for AI risks research, from former SIAI (now CFAR) staff member Anna Salamon. You might try putting numbers from these calculations in to a spreadsheet or Instacalc to get a rough idea of how the outputs change given different assumed inputs. Previous LW posts on Fermi estimates: 1, 2.