When I look at my Artifacts feed I see hundreds of nuget packages from Microsoft and other authors who's packages I use. Why are those packages stored in my feed? Looking at the billing page I see that my feed uses 1.96 GB. That is just below the 2 GB threshold after which I will be billed. Of the 1.96 GB in use, maybe 10 mb is actually used by packages I create.
How do I remove the foreign nuget packages and prevent them from being stored in my feed?
Check (and remove if desired) Artifacts > Settings > Upstream Sources.
In most cases there is no need to use these, but there can be some benefits, the main one being that if an upstream version (or entire package) is removed, your package will still have access to the copy that Azure will have made for you.