Since 1994, eight teams made the playoffs each year, 6 division winners and one wild card from each league. In 2012, this format has been expanded to add two more wildcard teams, one from each league, so there will now be ten teams in the playoffs. There will be one wildcard game in each league, then best-of-5 series to eliminate two of the four remaining teams in each league, then best-of-7 league championship series, and finally the best-of-7 World Series. So, a team could play as many as 20 games in the postseason (or as few as one!). http://en.wikipedia.org/wiki/Major_League_Baseball_postseason
As teams are eliminated from the playoffs (according to the MLB website), either duing the regular season or during the postseason they will be closed out at zero.
This may be harder than is apparent at first glance. "On the last day of the 2011 regular season, the post-season fate of four teams across both leagues was decided." This quotation and most of the statistics I used to analyze this question came from http://en.wikipedia.org/wiki/2011_Major_League_Baseball_season
In 2011, a total of 38 postseason games were played and a total of 371 runs were scored; just under an average of 5 per team per game. Total postseason runs were as follows: Rays 21, Phillies 21, Diamondbacks 25, Yankees 28, Tigers 42, Brewers 49, Rangers 85, and Cardinals 100.
So, allowing for the extra wild card games, I have assumed that each team now playing will score an average of 13 runs in postseason play. Given that there are 30 teams, that would total 390 points, only slightly higher than last year (remember, there will be two more games this year, with the wild-card playoffs).
Of course, given that we are nearly halfway through the season (most teams have played 71 to 73 of 162 games), some teams are more likely than others to get into postseason play. I have done my best to reflect those chances in the starting prices, but obviously that is a bit arbitrary, and I'm sure my fellow Inkling players will adjust them if needed!
Also, I have set the scaling to 10, instead of 20 as has been done in prior "points" markets. My hope is that this will allow more people to play, without giving total power to a few to set prices. We'll see. If that doesn't seem right once we get going, I can always refund and start over, but I hope it won't come to that! Good luck!
There is currently no information on mlb.com about the postseason schedule. When that is announced, I will adjust the closing date of this market to end sometime before the last few games (suggestions as to exactly when are welcome).
*October 8 update:* now that the schedule has been announced, I set the end of trading to be after the 2nd game of the World Series.
Going forward, all deciding games will be uh-ohed to scheduled starting time plus 2 hours.