When these were installed in Portland some years ago, I distinctly remember telling my friend there "this may be convenient, but once you let these meters in, you realize, they can charge you whatever they want."
While not the case in Portland, where these bastards have been installed in L.A. the rate for parking has "magically" gone from a reasonable $1.50/hr to $4!! per hour. You see, where once a dollar or $1.50 was "reasonable" for a person to pay in quarters, once the debit system is used, well, The Sky Is The Limit. L.A. has, for the moment, the highest street parking rates in the nation. That is until some other city installs these bastards and charges whatever they damn please for street parking.