There is often talk of this or that job being 'exploitative' or of people on low wages being 'exploited' by their employers, as if there were something deeply unjust about paying someone poorly. But this misses a fundamental point about injustice. You cannot be unjustly treated voluntarily: if you agree to the action, you are not being unjustly treated. Anyone who accepts a job, regardless of the pay, is not being unjustly treated by their employer. Obviously this does not apply to someone forced into a job against their will. But if they have accepted their job, even if the reasons pushing them to accept it might be deemed unfair in a wider sense, the act of employing them cannot itself be deemed unjust.