This is a policy adopted by some organisations(usually socialist or left-of-centre political groups)where members of that organisation agree to never accept wages higher than the wage of the average working class person whilst being employed by that organisation.
For example the Socialist Workers Party (UK) might agree that should any of its members be elected as MP accept a wage of more than £20,000 a year. This would stay the same even if that person was appointed to the Cabinet or even Primeminister.
This idea is based on the idea that politicians (or trade union officials)are there to serve the people of the country rather than earn themselves a fortune and/or raise their status. (also known as careerism) Proponents claim that high wages for politicians are a waste of taxpayers money and raise the politician above the rest of the public. High wages will alienate them from the working class and become a distraction from their task of public service.
Some religious organisations also adopt a similar policy. Many Christian churches for example point to the Gospels of the Bible where Jesus humbled Himself and became a servant to His followers. Many churches pay their clergy low wages because of this. However some big churches have been criticised for paying their Pastors/ministers very high wages.