Holiday Rares were dropped on holidays, from some stronger bosses in the world or received from higher level Treasure Trails.
For the most part rares either hold their value or grow, just like a stock. They have now become the most expensive items in the game, and those runescape accounts for sale with a rare holiday item can value a high price! Holiday Rares are items that were dropped on holidays to give characters some rewards for good performing. Runescape rare items were introduced into the Runescape marketplace for a single day to celebrate a holiday, so they are named for holiday drops. Jagex has extended recent holiday drop periods to two weeks. And then Jagex decided that the introduction of these rare items was detrimental to the Runescape economy. It is speculated that banned runescape account's rares are added to the grand exchange as the high demand from players.
Why not buying runescape accounts which hold a Holiday Item?