If you could somehow trade your used games this might be something. Buying an extra game just so you can trade for some hat...well, not my cup of tea, but apparently the cup of tea of very many other people.
When I learned that there is a brisk business in hiring Chinese people in order to grind the early MMORPG levels, I am not surprised by anything about in game purchases.
It's all about trading up. Buy the popular packs when the games are the cheapest and than trade the extra copies for higher value games down the road. You can save quite a bit of money this way if they continue to let it happen.
trading used games would be counter-productive because steam doesn't get anything out of it.
you're essentially paying for only a game, but also getting free currency if you trade that game when you get bored of it.