Serious Eats: Talk
Cost of Cocktails at Bars
Tried to post this repeatedly at the article and it went straight to moderation.
Often the ingredient costs represent 20-30 % of the final cost. In other words, if the drink costs $2 to make, multiply by 5 = $10 final cost. Your margins may vary. Unusual factors may add to cost--live entertainment, for instance.
Food Service Warehouse has a primer online on "how to price alcoholic beverages" for those interested in an intro.