Glad to chat with someone who understands in-game economies. I agree, but for a different reason. I don't think Valve cares about the economics that much. I think it's more of a product strategy move.

They have been threatened numerous times with lawsuits over the gambling aspects of the IAP. This moves completely de-risks that. As you said, it's not going to affect profits very directly. It will however make the speculative market collapse, and keep players engaged within the game's economy.