[msandford]

The big money saver would be the engines. Most big helicopters run on turbines and they are not cheap. And they have a limited lifetime before you're legally required to overhaul or replace them. For the engines on business jets that a friend of mine used to charter pilot, that number was between $500 and $1500 per hour.

If you built electric motors for a chopper you could theoretically design so that it had 8 motor any one or two or three of which could fail and still fly. Make several different independent battery packs and you enjoy more robustness. If you engineered it right you could make the case to the FAA that the helicopter doesn't need any expensive preventative maintenance on the motors or batteries, just on the drivetrain. Which would save a lot of money.

EDIT: "most helicopters" to "most big helicopters"