I am working on a brand new SaaS web application and need to estimate the initial bandwidth usage. Since the site doesn't exist yet, and since this is my first endeavor of this sort, I'm not really sure how much bandwidth to estimate to begin with.
We will be using Linux, Apache, PHP and Mysql.
The content will be generated dynamically. There will be images as part of the site design but user's will also upload images that will be displayed and documents that will be stored for download at later times.
We'd like to be able to support 500,000 page loads per month with estimated image loads being about two to three times that.
Since the site isn't built yet, we're looking for suggestions on how to create a good faith estimate for what we'll need at a minimum to launch the web app.