Besides, with open source you have more than just the original developer on whom you can use cash to entice him to make your favorite changes.
Effort spent on tools != effort spend on adding some feature I'd like on a programmer's editor. I could just switch to something better.
Plus, you probably overestimate how more productive a tool like a programmer's editor makes you.
The truth is an editor can make editing less repetitive, but it's not like an order of magnitude better. Not even 2x or 3x more productive. Thing is, there are very successful programmers using all kinds of editors, from Emacs and Vim to Eclipse (notch), to Textmate, to Notepad++. And tons of classic unix programs, including C and Unix itself, were written in ed or similar primitive editors.