[Sheriff Fatman]

The reason is the bigger increment in prize between 1st and 2nd compared to 2nd and 3rd.

Consider an 'average' player finishing in the money with an even distribution of 1st, 2nd and 3rds (we can assume his finishes are in proportion with his stack position). If he plays to maintain his starting position then on average he will win $33.33 in accordance with your calculation.

Now suppose another player takes a shot at finishing first each time he's short stacked or 2nd in chips, risking 3rd place by doing so and plays to conserve his 1st place when chip leader. Even if he's successful only half the time he's not chip leader he wins (2/3*50 + 1/3*20) = $40 on average.

In other words the incremental increase in profit from converting 3rds and 2nds into 1st places is higher than the decrease in profit from finishing 3rd when starting in either 2nd or 3rd position.

If the increments in prizes were equal then this would not apply - there would be no difference compared to trying to maintain your starting position once in the money.

Therefore there are 2 key goals to these SnGs
1) Make the money
2) Once you're in the money, try to win even if you risk finishing 3rd doing so.

Sheriff