That's why it would be an editor. Allow the user to choose the level of the financial prosperity within the league. Those who are not concerned with historical "accuracy," can still use the "Modern Era" financial gameplay settings in 1900. And for those who like something different in their leagues (and I've seen this brought up before) they can use the "deadball era" financial settings in 2002 to give their league a small market or minor league feel to it. It should be totally customizeable as well, where users can give the "average" figures for that era, and the game goes based on those - as it does with the hitting era now.
Catagories could include attendance averages, ticket cost averages, television (or radio!) revenue, and player salaries. Salaries could be broken down further into a minimum salary, salary for an average player, and salary for a superstar. If you have the ability to customize those, you can have leagues where you decide if the top players' salaries are much more than or much closer to the other players in the leauge. Given the way Markus handles something as complex as the hitting era settings, financials should be easy (easy for me to say ), and would add alot more realism for alot of people. And if it does nothing for you, don't use that feature!
