Exactly. I almost never pay full price on Steam, and I add a lot of keys from Humble or Fanatical bundles where I only intend to play half or so.

So yeah, I’m guessing it’s actually 10% or so of that figure if we make a few rules:

• count bundles as a single game, and if one game is played from it, that counts for the whole bundle
• assume games added to Steam are part of a bundle (perhaps in groups of 5)
• don’t count games that were ever given away free
• assume all games were purchased at a discount

That would probably get us pretty close to the real number.