The controller is currently sold out on the Microsoft Store site, along with other retailers like Best Buy, Walmart, Target and more. Technically, the controller is available to buy on Amazon, but its only from third-party suppliers, and at prices that are nearly double the current suggested retail price.
VentureBeat got a response to the current unavailability of the Xbox Elite Wireless Controller from Microsoft:
"We're thrilled at the amount of interest we've received for the Xbox Elite Wireless Controller. We are working quickly to get more units of the Xbox Elite Wireless Controller in the hands of fans, and look forward to replenishing inventory in time for the holidays."
In addition, Xbox leader Phil Spencer posted his own comment on the controller and its status on the NeoGAF message boards:
"We are definitely pleasantly surprised by the consumer response to this product. The controller was designed for a niche consumer base, for the hardcore and pro players. We did not expect the demand that this controller received. We do plan on increasing production of the product to meet consumer demand. On another note, I'm pleased to be reading the positive impressions from you guys. Really glad you guys are liking this controller!"
Microsoft has yet to reveal any concrete sales numbers for the controller.