A robot bartender will cost lot more than a human one. Makes no economic sense
It depends.
Robots you pay for once. Humans you pay for continuously. Once you buy the robot then it doesn't get tired, it doesn't ask for a salary or sleep.
If you use a robot for one year it will likely be more expensive then one years salary for a bartender.
You will still need to pay for things like repairs and electricity for the robot. If you are paying the bartender only $2.13 per hour then these expenses would potentially exceed what you would pay the bartender.
A robot will also not be able to effectively upsell and encourage additional sales the same ways that a human can.
Solar electricity can power robots so I don't think electricity is the issue. I think repair can be made by letting robots make a profit and pay for its own repairs with its savings.
I do think robots eventually will be dramatically cheaper for the service industry. It will start with vending machines and slowly progress to robots.