That's not so bad; why not cut the battery draw in half by pulling from the wall circuit in parallel? 120WH in power tool batteries would cost ~$170-$180, so we can imagine a $200 kettle. Expensive, not a mass market item - but give it a few more years of continued battery improvement, and maybe this could happen. The base would certainly be much bulkier than that of a normal electric kettle, but it would still be smaller than the base of an average blender, so not unreasonable for a North American kitchen.