The analogy is that there are things that can't be sold and bought. Which is for many people starting to be an incomprehensible concept because of the totalitarian market ideology of our time.
The worst use of analogy in my view is to use it not for improving understanding, but for morally loading the subject with the baggage from the analogy. When you say that data is like organs, you are morally loading all of our worst perceptions on what organ trade can be (harvesting, trafficking, and exploitation crimes) onto data.
Data resale is serious for different reasons, and trying to morally load it with organ considerations is obfuscating those reasons. We should instead understand those reasons for data itself.