Your son's argument seems confused. Taxi drivers in the US typically aren't unionized and their mandated "livable" rates are mostly eaten up by medallion rental fees, which freely adjust on the market, and are bid up to the point that it only leaves behind the previous unlivable wage for the driver.

(It turns out that "having an expensive final product" doesn't mean that every contributor's market value is expensive. Who knew? I mean, other than people familiar with the concept of economic incidence.)