Wigwam as far as i can make out (and prices vary from car to car) EVs are around 30-40% cheaper to service than ICE cars.
Servicing BEVs is a bit of a new science so times between servicing will almost definitely change. Its likely that servicing will be required between 10,000-15,000 miles, but will likely increase as info is gathered.
Servicing is only part of the mix though as there are many, many, fewer parts and bits and pieces to go wrong and parts for an BEV will almost certainly be cheaper than for an ICE car.