Google confirmed that the service Project Fi will cost $20 a month for basic plan which include talk, text, Wi-Fi tethering and coverage in 120+ countries. Users will have to pay $10 per month for every 1GB of data you desire. Good thing is that if you do not use all your purchased data in a month, you will get the refund for unused data.
With this service, company claims to offer best network wherever you go. Google has partnered with Sprint and T-Mobile. Project Fi will automatically connect you with the network having best coverage at your place.
Project Fi service is currently invite-only. If you want to try, you can request here.
Source: Google Blog