I work in food service, with tips I average more than minimum wage. If minimum wage rises I will make far less than I do now. Prices will rise and business will fall. Those who do come to the restaurant will be annoyed by the price hikes and tip less.
My guess a 30% increase the price of a Big Mac will not hurt sales one bit. Also at $15/hr the employee is no longer eligible for govt. handouts so. My guess it is a wash.