How to estimate storage and traffic used for docker images in AWS ECR?

I'm trying to esimate monthly cost of using AWS ECR. It will consist of: outgoing traffic cost (downloading images) and storage cost (storing images in ECR).

Let's assume, that:

• We are building some web service using Mono (base docker image size is 500Mb);
• Our CI&CD server builds and pushes images to ECR 300 times per month. Old images not removed for simplicity;
• Our compiled code adds additional layer of 40Mb to base image;
• We download images 60 times per month from AWS;

The 1st question is: how to estimage monthly storage volume? What equation is correct?

Monthly_Vol_1 = 500+40*300; - base image stored only once

Monthly_Vol_2 = (500+40)*300; - every image includes base image

The 2nd questions is: how to estimate monthly traffic from AWS? Let's assume, that host downloading images does not remove existing data.

Monthly_Traf_1 = (500+40)*60; - every time it downloads base image and additional layer

Monthly_Traf_2 = 500+40*60; - base image is downloaded only for the 1st image. Only application updates are downloaded

Monthly_Traf_3 = 40*60; - base image is downloaded not from AWS ECR, but from docker hub

UPDATE:

I uploaded 2 images to AWS ECR in September and checked billing info after 2 months. What I discovered:

It cost me $0.04 monthly just to store 2 images (without transfers). According to AWS ECR pricing ($0.10 per 1Gb storage) looks like Amazon stores 400Mb of data. The same 400Mb I see in AWS ECS dashboard.

I tried to understand and calculate what data is stored (using docker image and docker history commands), but failed.

I have 2 docker images uploaded to AWS ECR:

1. SVC (482Mb) based on Mono (409Mb)
2. WEB (679Mb) based on Node (634Mb)

If AWS stores full images, then it shall store 482+679=1161Mb

If AWS stores just added layers, then it shall store 45+73=118Mb

How AWS calculates 400Mb? O_o

UPDATE2:

Looks like AWS stores full images, but compressed (400Mb instead of 1161Mb). According to http://docs.aws.amazon.com/AmazonECR/latest/APIReference/API_DescribeImages.html

Beginning with Docker version 1.9, the Docker client compresses image layers before pushing them to a V2 Docker registry. The output of the docker images command shows the uncompressed image size, so it may return a larger image size than the image sizes returned by DescribeImages.