I have a 20 game package and they let me add more yesterday the 23rd.
That said here is what I paid for post season tickets (They have me in section 114, slightly worse then regular season but i'm not complaining)
ALDS: $81/seat
ALCS: $140/seat
World Series: $266/seat
Parking for all games was $30
Edit: Also i dont think you get guaranteed postseason access with only a 10 game package. I think you need 20/40/or full season. Someone can correct me if I'm wrong.