Calculating Return on Investment for Any Developer Tool
I just finished work on a spreadsheet to calculate the ROI for developer tools. I've got it pre-configured to calculate ROI for a $249 CodeRush and Refactor! Pro purchase (with a corresponding 25% increase in coding speed), but you should be able to use it for any dev tool on which you're trying to get buy-in from management.
Just change the red values to something more applicable to your situation, and you can get a sense of how much product usage time would pass before you saw a return on your investment. Here's a screen shot of the spreadsheet:
One neat feature of this spreadsheet is that it's flexible in how you measure productivity. In the example above, we're measuring productivity in methods written per hour (that's the value of the "Unit of Code" field. If you would prefer to calculate this based on lines of code per hour, or some other metric that feels more comfortable, it's easy to adapt.
UPDATE: Revised spreadsheet and post is here.