For $12 million, you can get a star wide receiver in the National Football League. Or a starting Major League Baseball pitcher. Or, based on its assessed value, downtown Buffalo’s largest (and virtually empty) office building. In court papers related to its complex foreclosure case, the 38-story One Seneca Tower is now assessed at just $12 million, a drop of 67 percent in the past year. The reason is that more than 95 percent of the 44-year-old, 851,000-square-foot building is unoccupied. The…