My son was circumcised by his father. Who's not a doctor, just cheap.

The line is structured as a darkly comic one-liner: it begins with a startling claim (a father performing a medical procedure) and then pivots to a blunt punchline that reframes the motive as penny-pinching rather than expertise. The humor relies on incongruity and shock, using the taboo and risk of circumcision to satirize extreme frugality and poor judgment. Implicitly, it critiques the idea that saving money justifies bypassing professional care, and it exposes how “cheapness” can become a defining trait that overrides common sense. The clipped final clause (“just cheap”) functions as a moral verdict as much as a joke tag.