The purpose of the update is certainly not to reduce the cost of these items, but to better position Valve to earn this revenue steam, as opposed to third party scalpers. Looks like it's working.
They don't care about the resell value since they don't earn a commission on those sales.
The point is that, for as long as items can be transferred in game, they are always convertible to cash in the real world. Inserting artificial friction inside the game to increase scarcity, such as limiting convertibility of items, will drive those trades away from the game economy and into the third party ecosystem where the dollar rules supreme as the super-convertible means of exchange. So you have an induced scarcity that in effect drives third party profits.
By increasing in-game convertibility, the trades are directed to other in game assets that are a just a proxy for loot boxes, i.e money in Valve's accounts. So prices crashing in the third party market signal that players have a cheaper and more direct route to acquire them - give the money to Valve - which also generates the supply of new rare items as those loot boxes are opened.
It's a smart economic move.
Buy that doesn't mean the prices will stay low, since they can always control the overall scarcity, or add new, rarer and more exclusive items. The total amount of money they extract from "kids" is ultimately linked to their ability and willingness to pay.
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.
