Raising prices by 1.3% also has some impact on sales. In theory it should be greater than 1.3% (or else why hasn't the restaurant greedily raised its prices already). To get higher wages for the workers you need one of two things.

1. Go upmarket in some way, either sell nicer food with a better margin or higher more oroductive employees.

2. Through collective action of some kind get all competitors to raise their prices and pass the cartel profits to the worker (for instance a minimum wage law could accomplish this).