MLB controls all postseason tickets. They will allow teams still in contention to print and distribute tickets. MLB also sets the price, based on seating. I would say half of the tickets go to the fans (season ticket holders) and MLB hold back the rest.
Friend of mine had two for games 1-2 of the Detroit/Cards WS a few years ago. Sold his 2 on Stubhub for $2800 for the pair.