Thank you for giving so many valuable suggestions.
* My few hired some professionals and they told me that it's really difficult to actually find those, who actually care to reduce your AWS costs. There are few third party tools in the market that gives budget alerts, daily cost of service breakdown etc. when integrated with AWS account? Have you tried any of those and how is your experience?
Actually I had an unused instance and it took me quite a lot of time to actually figure out that this was the actual cause. I do check the prices but with so many deep learning projects, it's actually really difficult to figure out.
Have you tried any third party AWS cost optimization tool ?