free drinks?

So I told my friend that casino's give you free drinks if you are playing. If you are not playing then you pay for it. I also said but leave a good tip. He then said that the cocktail waitress actually pays for the drinks that she gives to you for free and in return she will get a tip from you. But she does not pay full price for the drink. So i told my friend this: So you are saying if i order a $3.00 drink, and get if for free because i am playing craps, then i give her a $1.50 tip, then She would give some of that money back to the bar? He said yep. This doesnt make sense. I am under the impression as long as you are putting in money down on the tables or slots then you are getting free drinks. Its like you are paying for your drinks anyway since you are just dumping money in there right? Who is correct?

Rudy