+1 on the mad scientist thing. But seriously, I've gathered a collection of chemicals (mostly from Artcraft, some from Formulary, a few from "odd" places) and I can now mix up pretty much any B&W developer I might want from Anchell's Cookbook (at least when I have fresh glycin) or Jacobsen's Developing, not to mention more than a few color processes, and B&W reversal. Once the initial outlay has been made, the cost of mixing a liter of a new developer to see what it can do is minimal, and keeping the few that I regularly use (D-76, ID-68, Ansco 47, Mytol, Parodinal) along with their respective replenishers (if I want to replenish) couldn't be easier. I consider the cost nominal, definitely less than packaged developers, and I can mix exactly the quantity I want. Sulfite is the only thing I need to reorder regularly, but that's an opportunity to add a new chemical or two to my arsenal. I mostly use Hypam fixer for everything (even color) and I wouldn't have a clue how to even start to build a Leica, but I can damn sure mix up some developers.