Settle down, this is not an insult. I've worked for a lot less than that. It's just that there are people who want to go places, do things, and grow, and there are people who are perfectly content where they are. Someone who is perfectly content at $15 an hour isn't going to give you $20 an hour worth of work just because you pay them $20 an hour. They're going to give you 15.
I have zero problem with people who are content working for $15 an hour - I'm related to some of them and love them very much. I just don't want them working for me. If you have goals and ambitions, know you can do better than where you are today, and WANT to do better, let's hear it. What are you doing and why? What do you want to do? In a restaurant how can you add more value than you take away and help be the glue that keeps operations together?
Are you a 20 or are you a 15?