Sanitation workers may be low-skill but they are high-value. I don't think this is a good example.

In contrast, a friend of mine recently hired the teenager next door with cash (for less than the local minimums) to do some manual yard labor. This job simply wasn't worth paying for at a higher cost; my friend would have left the work un-done. But in this case the value proposition at a lower price was acceptable and the neighbor was glad for the extra cash.