Carbon neutral is kind of the 'whole enchilada' and like many 100% efforts, the last few percent cost the most. I don't know the actual cost breakdown, but if we assume the pareto principle applies, we will probably get a great amount of benefit for doing 20% of that investment in the most polluting industries.

Saying it will cost $1T a year is just FUD from that perspective. Sure, doing it all will be very expensive, but if doing most of it is a hell of lot less expensive, why scare everyone by covering the 'worst case scenario'?