I feel like it's a false analogy to compare Spotify Streams to CD sales. For a fairer comparison, you should measure against something more ephemeral. The biggest radio channels in the US have a few million listeners each. Let's say your record does ok, and gets airtime on a few second-tier radio stations. For easy math, let's do 20 plays * 50,000 listeners per play. This also gives you a total of one million listens…
Spotify is closer to CDs than radio because you can play any song you want whenever you want at a quality similar to CDs.
Trying to stuff the new-world of streaming into the old-world boxes of CD or Radio just doesn't work. the world changed.