Our team recently launched the ability for you to be alerted about AWS pricing changes for existing EC2 instances as well as alerts for new instances being launched and what their associated pricing is.
We've had this on in the background for a few weeks and it's alerting for new instance types faster than AWS' blog posts hit. Also whenever anything changes for existing EC2 instances you can see as soon as it changes.
If you want to set an alert, you can see this here: https://newsletters.vantage.sh/