Let's remember first and foremost this is a business. As an owner you must make money. I can't speak for everyone out there but most baristas are younger, and most don't stick around to make it a career. Therefore, I can't see paying anything more than minimum wage, except for someone you may want to manage your location, whereby they are responsible for the operations of the location including, ordering weekly supplies, compiling the paperwork, making deposits, and sometimes holding employee meetings. If the employee takes pride in what they are doing, it will show. Owners (if fair) will reward by offering higher pay after a certain period of time, bonuses, etc. But to assume that one can walk in the door and receive more is not realistic. At our place we don't consider someone a "Barista" until they have at least 1 year experience in drink prep, basic equipment ops, including being able to know basic troubleshooting, customer service skills, and basic management knowledge (knowing managers job) to fill in in case manager is on vacation, or if promoted. If they continue to make themselves better and not assume that they know everything after being trained once, they have a better chance to grow, and will appreciate what it takes to become successful. Maybe in the future even open their own location with the necessary skills to be successful. We've done just that with a few of our ex employees, and today they see why we insisted on the way things were.
I've visited far too many espresso businesses where not only did the drink taste bad, but the customer service seriously lacked. Sometimes I wonder if the owner of the business was trained properly themselves, or do they ever visit their own location. I say this only because our industry should grow and become better, not worse. Through years of experience and making mistakes in the past I can only offer what has worked for us.
With all of that being said, the grass is always greener on the other side, meaning if you don't own the business, it's always easy to say you are not being paid enough. Try to run the business yourself and see if you still feel the same.