they could ezpass the free east side bridges and achieve the same desired effect (more money, less traffic into manhattan) - but the traffic backups from the toll plazas into queens and brooklyn would be massive.
manhattan is already a place where businesses operate with employees who live no where near their places of work. at some point, businesses and their workers will simply have too many burdens placed on them to continue supporting this practice - and will realize its easier to relocate to where the workers are anyway. the problem with that is, all of the NY mass transit is designed to get workers from the suburbs - to Manhattan. as more businesses move to NJ or the outer boroughs - the only way to get to work there is by car. so strangling manhattan and forcing businesses to move, just pushes more people into their cars in the outer locales, and off mass transit.
what they really need to do is gut the MTA and the LIRR - they are bloated, inefficient, the service is poor. if mass transit were better, cheaper and faster - less people would drive.
If more businesses relocate to NJ, watch NY eminent domain NJ.