This is a quick and dirty to scan the EC2 and RDS instances on an account, and by no means is using best practices for parsing json.

aws_scan.sh

while read -r region; do
    printf "%s:\n" "$region";
    aws ec2 describe-instances --region "$region" | \
        awk -F '"' '/InstanceType/ {print $4}' | \
            sort | \
                uniq -c;
    aws rds describe-db-instances --region "$region" | \
        awk -F '"' '/DBInstanceClass/ {print $4}' | \
            sort | \
                uniq -c;
done < <( echo 'ap-northeast-1
ap-northeast-2
ap-south-1
ap-southeast-1
ap-southeast-2
ca-central-1
eu-central-1
eu-west-1
eu-west-2
sa-east-1
us-east-1
us-east-2
us-west-1
us-west-2')