When the city was upgrading, it was claimed in the news that there was a lot of damage to the mechanical meters from people trying to steal the coins. This resulted in excessive maintenance costs and under utilized parking spaces.

Also, while the trucks and other associated materials would be expensive, the labour should be significantly cheaper. Less people are required to enforce payment, as the trucks drive down the street without anyone stopping to issue tickets.

I guess the economics would be beneficial in the long run.