Betting vs calling with a draw

[NYplayer]

Another way to think about it is like this. You're going to win your share of what's in the middle whether bets go in or not. So you shouldn't base betting on what odds the money already in the pot is giving you. you need to be sure that you are getting more than your fair share of the new money going in in order to desire betting.

quick example. imagine given a certain # of outs you win 1 in 10 times and there's $500 in the pot in a 10/20 game. imagine betting stops on the turn.
if you check you know he'll check. you'll win 10% of the 500 or $50.
if you bet $20 he'll call and you'll win 10% of $520 or $52. however, you have to subtract from that 90% of the $20 you invested on the turn because you'll lose that 90% of the time. so that's worse then the $50 you'd earn by just checking. you aren't getting your fair share of the new money going in so it's bad to bet. even though the pot at 500:20 or 25:1 is better than your 10% (or 9:1) chance of winning.