Google Cloud BigTable pricing is based mainly on storage type. If your requirement is 1 node, and the server is running 24 hour per day, 7 day a week, and you use SSD storage of 1 TB per month, then your average cost would be USD $650 per month. If instead of SSD you use HDD storage, keeping all other requirements same, then cost would be reduced to USD $500 per month.
Egress from Google Cloud to the internet for Cloud Bigtable is charged at standard networking rates.


You can use https://cloud.google.com/products/calculator for putting in your exact requirements and get a better estimate.
Some types of network egress traffic are subject to bandwidth charges, as shown below.
Ingress | Free |
Egress to the same zone | Free |
Egress between zones in the same region | Free |
Cross-region network egress to the same continent (per GB) | $0.01 |
Inter-continental egress | At Internet egress rate |
For more comprehensive details on Google Pricing, please refer below link. https://cloud.google.com/bigtable/pricing