Hello @sanmi thanks for leaving a great comment. I agree with you water a free resource is getting more expensive as time goes by simple solutions like this when applied will help curtail this trend.The product is past the concept stage as they claim with these statement on their site

RESEARCH / FINDINGS
Based on the designs of the existing rooftop water tanks, we have created a simple device to collect these two valuable natural resources to meet the needs of electricity and drinking water.

The price i believe should not be too expensive.I will try to hunt for the price and where to buy so i can update the post also found a picture that shows it is currently in use in mexico