Here is a place with some info. Perhaps you have all ready found it.
EH.Net Encyclopedia: The Economic History of Major League Baseball
I tried playing with this a couple of years ago. Made some revisions to the financial.txt file but the results were just as unrealistic as with the existing file. Different but unrealistic.
I think there are some underlying formulas in the game that get applied to the data in this file but could not find anyone that knew anything about.
I would be more than willing to help on this but at this point I am really stuck with what to try next.
This is an area that I would really like to see improvement in the game.