Media Rights and Market Size

Last week, Larry Granillo found an old article in Sponsor magazine ("the national weekly of TV and radio advertising") that listed the TV and radio deals each MLB team had in place for the upcoming 1961 season. The chart is here, and is pretty cool on its own. Larry did a good job breaking down who spent what where, but I was personally more interested in the "why". Several companies (like American Tobacco) sponsored teams in multiple markets; how did their advertising agency decide to pay $140,000 for a third of the Red Sox' rights, but $200,000 for a third of the Tigers' rights?