&gt;  The total value of all items I&#x27;ve earned on Steam probably doesn&#x27;t even sum to 1 Euro...<p>You aren&#x27;t idling Bad Rats then, if you just idle the game you&#x27;ll earn $0.20 cards every so often. There&#x27;s a really weird underground economy in steam around cards. I don&#x27;t really understand the market, it seems akin to smokes in the joint. There are farmers (people idling games), scammers (people taking more value than they&#x27;re getting), there are arbitration scripts always running for the various steam and third party market places.<p>A lot of the value I think comes from people who want to have a really nice Steam profile. With enough cards and xp you can get a nice background and a high level. I haven&#x27;t really looked into it but some people take it really serious and are willing to pay for it.