When Knight of the White Orchid was reprinted in Magic Origins it saw very little play, and was worth about a buck for a long time. Then Shadows Over Innistrad rolled around and suddenly white is the best color in Standard, and a white aggro deck just won the SCG Invitational. Knight of the White Orchid is one of the stronger role-players in Human Aggro, and as such it has seen substantial price movement.

When looking at the price of this card, its price trajectory is based on whether you think that white aggro will perform as well on the Pro Tour as it has on the SCG Tour. Two weeks of finals appearances sure drives demand for a card. I would like to think that the pros have enough imagination to defeat an aggressive mono-white deck, though there is precedent for white aggro dominating a PT with Tempered Steel in Scars of Mirrodin block. If you keep throwing things at a deck and it keeps winning, there's not much you can do about that.

Personally, I'd be amazed if Human Aggro wasn't a solvable problem, though I admit that the deck is stronger than it looks. Holding onto these cards is a gamble on PT success, and personally I'm happy buylisting my copies. That said, if this deck puts a couple players into the top 8 of PT Shadows, then I fully expect to see continued growth. It's a sell for me, but you're not crazy if you hold these or buy your set as a name pro cuts through the swiss of the PT with Human Aggro.