Why do people continue to use MM for "million", especially outside of the context of money?
It's not just finance, but in other contexts too, such as online marketing CPM = Cost Per Thousand.
MM then is used to denote a thousand thousands, or one million. In online marketing sometimes you'll see CPMM = Cost Per Million.
Unless you're a strict follower of the IEC standard, in which case k = 1000, and what I was talking about was a kibibyte.
Standards are hard. It's not just the Americans' fault
http://www.accountingcoach.com/blog/what-does-m-and-mm-stand...