What you pay depends on when you joined (later members pay more), but every once in a while they raise everyone's price to keep pace with the rising cost of new issues. I've been paying $108 for my PS models since I joined a couple of years ago, during which time the price of a standard issue model has gone from $115 to $120, and then to $129, an increase of $14.
DM has finally upped my preview price to $117, an increase of $9, so I'm still ahead of the game even though I'll pay more for mine now. Can't complain really, since I'm still getting a deal.