In Australia an 18kW system.installed with two 10kW/h Tesla batteries should run under $30,000 AUD installed. That's somewhere in the vicinity of $23,000 USD.

I've been looking at upgrading my rooftop solar in Australia, since we have had 5kW on the roof for close to 15 years now. Ill put away the pennies for a few more years and pull the trigger at a similar time to when we get our first EV / PHEV with V2G.