Do you remember your first holographic Pokemon card? I do, it was a Dewgong. I loved that card; it meant so much to me. In an apparent attempt to capture that same feeling, Valve has introduced Foil cards to its new line of Steam trading cards.
These cards are being sold anywhere from $10 to $70 on the Community Market. It doesn't seem as if people are actually buying them at the higher-end prices, but that hasn't stopped people from selling them. Protip: don't buy these for high prices, the prices will only go down as more are discovered each day and will eventually settle. I can see these being worth a lot in the distant future, though, as this edition of cards stops dropping and a set amount of them exists.
I'm not exactly sure why, but this whole Steam trading card business has gotten me a little too excited.