The savings implies they saved $2B over AWS. I can't read the article since I don't have a BI account, but unless they saved $2B over AWS (rather than $2B over their previous infrastructure) it's definitely misleading.

It is a bad title. The inclusion of "ignoring Amazon" implies that the difference between the using AWS and not using AWS is $2B. Otherwise, it makes as much sense to title it "Bank of America saved $2B per year ignoring shark attacks, building own cloud".