Well I just googled and Valve has 1,139 employees, and Spotify will now have 7,800 - It's nowhere near 20x.

Still a big gap, although I suspect they are very different offerings and companies. Differences include:

* Spotify needs to sell ads (to support it's free tier). This requires engineering and people to sell the ads.

* Spotify is in a more competitive market than Steam (who have a nearly de-facto monopoly) so more advertising/marketing effort is required.

* Interfacing with the entire global music industry takes time and resource.

There may also be differences to the extent these companies outsource and use contractors which could make it more difficult to see actual headcount.