The IPv4 address pool has decreased over the years, and as reported by AWS the cost to acquire one IPv4 address has increased by 300% the last five years1. Because of this and the gradual transition to IPv6, AWS is introducing a new charge, $0.005 per IPv4 address per hour for all public IPv4 addresses.
As a fun perspective, check out what IP address you are using on your own Linux OS (not necessarily Linux running in AWS).
ifconfig -a | egrep "inet|inet6"
The output will show you the filtered output from ifconfig, with the IPv4 (inet) and IPv6 (inet6) addresses that are configured.
- See the AWS News Blog. ↩︎