PBS' operating revenue in fiscal year 2004 was $333 million. Leading sources of revenue included: station assessments (47%); CPB and federal grants (24%); royalties, license fees, satellite services and investment income (14%) and educational product sales (12%).
So by these numbers, and I don't know exactly what CPB is or it's purpose but let us say, for the sake of argument, that 24% comes from the govenment (and I know that with grants PBS is only one of many applying for the money). So, that comes to about 80 million bucks a year.
I will say that there are liberal type programs on PBS, but there are so many other educational programs on this network that make 80 million worth it. Such as Sesame Street, the great documentaries like Ken Burns, Jazz, Baseball, or The Civil War. Not to mention awesome shows that really challenge people to think, like Nova, or Frontline. Maybe it's just fun and interesting like Antiques Roadshow. These are a small portion of the total programing, but I'm willing to pay for shows like these.