Exodus 30

When thou takest the sum of the children of Israel after their number, then shall they give every man a ransom for his soul unto the LORD, when thou numberest them; that there be no plague among them, when thou numberest them.
Exodus 30:12 KJV commentary https://bible.com/bible/1/exo.30.12.KJV

What is the point, that numbering the people of God was a trespass?…

Because it sounds like God is saying that if you allow yourself to be numbered you will be punished but the money will in a sense atone for it.

This reminds of when David chose to number the people and God caused a plague to fall on them.

https://bible.com/bible/1/exo.30.12.KJV