I just looked on Google. Current price is $9200 and if you are in the right area, Tesla installation is $1,100. I believe there is a tax credit in the US, that will help with the cost. 
Some areas in the US participate in Virtual Power Plants and if you are lucky enough to be there, the battery is a money maker because it can be charged when juice is free, or nearly so and sold back to the grid to compete with high priced peaker plant power.