Consider an inductive charging system like Magne Charge - it has a rather huge "coupler" coil off the vehicle and a corresponding slot on the vehicle and the coils in the "coupler" and in the slot are aligned perfectly parallel and brought close to each other. So it looks like a good old transformer.
Yet there's a huge box in each Magne Charge system (a wall-mounted unit) that most likely generates higher frequency current. Btw this box seems to be accountable for huge energy losses.
What's the need for that frequency increase? A good old transformer will run at the same frequency as mains - 50 or 60 Hz depending on the region - and have pretty good efficiency. Why would this slightly altered transformer setup need higher frequency?