It's not as simple as "people like making money". That's just one part of the job. People who pay more on their loans with increasing income will behave like

It's not as simple as "people like making money". That's just one part of the job. People who pay more on their loans with increasing income will behave like people behave when taxes go up - the pay will be comparatively less important when weighed against things like working conditions, commute time, and interest in the work.