Why does this friend in particular deserve an exemption or reduced rate? Why don't they do something like take the trains into the nearest NJ suburb and leave their car at the parking lots there, which will probably be free or much cheaper, since they're doing the opposite of most commuters. Then they'd avoid this and all of the other tolls, most of which are much more expensive, and would probably be faster too.
They're a visual artist that is often lugging around hundreds of pounds of supplies/fabricated materials/finished pieces/etc. If they just needed a laptop bag or something that'd be a different story, public transit would work for them. I think they're avoiding the tolls by just working until 2am or so every night.
I only brought this up to agree that there are definitely working class people that live in the congestion zone and happen to need a car, and the extra $200-300/month does have a real impact on their lives. It would be nice to have taken them into account a bit more.