oh, sure it doesn't stack up at £6500, no arguement there.
But I'm pretty sure that something more cost effective will come along - I've seen kit a lot better priced than that already, though still not quite convinced by it... and then offer it to high energy users, not average energy users, and I reckon the figures will stack up at some point in the near future.
but I'd agree, not at £6.5k or anything like it for domestic, it needs to be done a lot more cleverly than that to find a price point that works.
For my money, it's going to be a relatively small system that trickle feeds a few hundred watts back in through the evening and night to cover base load that hits that economic point first - it should have the advantage of maximising battery life by limiting the draw off rate, and not dropping too far down the charge on the battery.
But we'll see I guess....