Yes, the casinos do calculate the value of a player’s play and then comp back a certain percentage, roughly about 33% to 40%. According to my theoretical house edge table, the casinos assume a house edge of 0.75% in blackjack. So in your example the value of this play would be 0.0075×$10×60×3=$13.50. If the casino comps back 1/3 of the play then you could expect to get a comp worth $4.50. However, most places don’t like to fuss with such small comps.