Even without congestion pricing, the poor are the least likely to drive. Spending public money to subsidize driving (which we’re still doing on balance, even in Manhattan) disproportionately helps the wealthy.
IMO it would be even better if was an auction based system, maybe 24/7. That way if someone has an <= $8.99 threshold/need to drive, and they find a slot, they will. I think the static pricing will create a distortion in the usage, maybe having dynamic pricing (with a ceiling) would be smarter?