No one has to demonstrate anything. If an employee who makes 20 burgers feels they should be entitled to more than they can negotiate their value-for-value with their risk-taking employer, or they can go out into the market and take a risk by selling burgers for other than guaranteed ROI. To the extent that their product is valued, they will be able to exchange that value for other value.
'Value' is determined by us, living in freedom. When you buy a burger you are handing over value-for-value. If you pay 40 dollars for that burger, then that burger was worth 40 dollars to you. There are no emperors of value who determine how much a burger is worth, at least as long as we live in a free country.
When you go to your employer and say, "I will stick burgers in a bag for 7.50 an hour," that is value-for-value. If an employee and employer have both reached an agreement, then they have reached an agreement, and that is as good as it gets. By definition, it is perfect. Each has agreed to exchange value for value. If an employee agrees without believing that he is receiving value for value, then he is the fool. If an employer agrees without believing that he is receiving value for value, then he is also the fool. In fact, in exchanges for value for value, it is entirely possible(and I'd say the normal case) that both parties believe they are receiving at least value for value or even higher(ie, win-win), and that defines 'value.'
Well, when I'm declared emperor, or you're declared emperor or the citizens of Bangladesh are declared emperors, whoever is declared emperor, 'the' emperor will point his gun at us plain free citizens and declare for us all what 'the' OneSizeFitsAll National Uber-alles Price "should be" for sticking burgers in a bag. Until then, I'll live in Freedom, and decide what is worth what.
God save us from these puddingheads and their penguin armed grasp on reality.