As for secondary markets, a lot of season ticket holders sell tickets through the
http://www.ticketexchangebyticketmaster.com/ website that is advertised so often during games.
As a season ticket holder myself, my playoff tickets cost considerably more than the regular season, so yeah, these won't come cheap. Given I've had to sell some of my earlier regular season game tickets thanks to my son's baseball schedule, I've used that site above and regularly sold tickets for multiples of face value.
There are lots of seats owned by ticket agencies, and frankly, by fans who either can't afford the prices or are willing to make a buck. Seats will be available one way or another to those willing to pay. (and no, I plan on using mine.
)
btw, thanks for delurking.