Modifiers for drinks with different pricing?
What is the best way to add modifiers that are priced differently depending on the sales price of the drink being modified? I'll use scotch as an example:
Johnnie Walker Blue Label is $20 for a 1oz shot, $27 for a 1.5oz (Rocks/Neat modifier), and $35 for a 2oz double (Double modifier).
Chivas Regal 12YO is $8 for a 1oz shot, $12.50 for a 1.5oz (Rocks/Neat modifier), and $14 for a 2oz double (Double modifier).
It looks like I can't use the same general modifiers for each product as they would need to be priced differently. Is there a way to multiply the price of the original drink to get pricing for the selected modifier?
1oz shot = original price
1.5oz Rocks/Neat = original price * 1.35
2oz Double = original price * 1.7