Yes, it's wrong to say "we can spend that $3bn elsewhere".
That said, the $3 billion is not the full price tag (externalities, etc.) and the $27 billion is not the whole story (can we see your raw data please?).
That said, the $3 billion is not the full price tag (externalities, etc.) and the $27 billion is not the whole story (can we see your raw data please?).
I'm not sure which raw data you'd like, but if you can be more specific I'll do my best to find it.