Embedding won't eat any of your server bandwidth. All YouTube traffic will go through Google servers. However, your website / script will eat some bandwidth serving static content such as HTML, CSS, JS, Images, ... .
You can estimate how many requests will 5TB handle calculating for example homepage or watch page response size. The simply divide 5TB by that number and wuala, you've got number of requests you can handle with 5TB of bandwidth.
It's not accurate, only an rough estimate. We don't take in count caching and 100 other things.