9. Blue Party Hat - Runescape ($4,000)
Going from a juggernaut spaceship capable of conquering entire galaxies to something far more humble, Runescape's famous Blue Party Hat once set a player back over $6,500.
In 2001, developers Jagex decided to host a special Christmas celebration in Runescape, spreading the season of goodwill by dropping Christmas Crackers to players which, when pulled, would result in the winners getting items and the losers getting a consolation party hat.
Despite being nothing more than a bit of fun that wasn't worth more than a few pennies initially, the party hats were all completely unobtainable following the discontinuation of this promo. The value of these hats subsequently began to soar, far eclipsing the maximum value allowed at the in-game Grand Exchange marketplace.
Price estimates for the item still value the Blue Party Hat at over two billion Runescape Gold, with recorded sales roughly equating to over $4,000. And, with no other hats being introduced since, it seems these incredibly rare items will only continue to rise in value over the coming years.
Again though... it's a paper party hat.