...involved. Casinos tend to be VERY scientific and there is nothing mystical about comping. The actual math has to do with how much the casino can expect to "retain" from you (ie: how much they expect you to lose).

From what I understand, you can typically expect to be comped somewhere in the neighborhood of 1/3 of your expected loss.

For instance, if the casino assumes it has a 2% edge on you in blackjack, and you are a $100-a-hand player (average), and you play for 4 hours (at an average of 2 hands per minute), the casino's expected retention would be $2 per hand or $4 per minute... times 240 minutes is $960. You should expect a comp in the range of $300 for that play. Playing at a $25 level for this time period should get you comped about 80 bucks worth.

Now, I'm sure all of the numbers in the equation vary from casino to casino, but I've read that this is the basic concept behind the valuation of comps.

Additionally, I don't believe that the casino factors in whether in you are winning or losing, since this has nothing to do with their expected rate of retention. The only exception might be if you've won a jackpot of some kind, since that might induce one to raise their level of play.