Came here to say the same thing. It's not even certain it's feasible, let alone put a price tag on it.

In which direction?

Upwards - It would probably take more than $1 per person!

I'm assuming the number was originally a guess at the money that would have to be poured into research to achieve RE < C, because less than $100 per person for a total switch to renewables is clearly wrong. That's a bit too handwavey to be included amongst other hard figures on a graph like this though.

Yes, it's a bit hand-wavy. Though after RE<C the transition is essentially self-funding.