I have been searching for an appropriate proverb which describes the status difference between a king and peasant/commoner, or in other words, a proverb that states that there is no comparison between the economic conditions of two said people.
Rosalind Fergusson, The Facts on File Dictionary of Proverbs (1983) lists several potentially relevant proverbs on the theme of status difference between king and commoner or between rich person and poor person. As far as I know, none of these expressions is in wide circulation today.
When the prince fiddles, the subject must dance.
The pleasures of the mighty are the tears of the poor.
The rich man has his ice in the summer and the poor man gets his in the winter.
The rich man may dine when he will, the poor man when he may.
In each case, the point of the proverb is that the king or rich person enjoys freedom and autonomy, while the subject or poor person is driven by necessity and obligation.