You definitely could, but that will increase costs even further. You're potentially replacing all your lighting, climate-control, water heating, cleaning (dishes/clothes), cooking & fridge/s to be more energy efficient also.

Actual power storage is a reasonably small cost (probably < 20%) in even the solar, power equipment (inverter, switches, controllers, etc), power-storage equation anyway if you want to go completely off-grid. So why does this product make anyone more likely to switch than the existing options?

Going off grid isn't something one does lightly.

Which was my point :).

You seemed to be suggesting you could just buy 2x $3500 batteries and go completely off the grid.

Obviously you can't go off grid without a solar system, what would charge the batteries?

To quote from the original post:

"Solar panels are cheap enough you only need batteries to last one night, as you can size the array to operate your loads even on cloudy days."