Are you surprised?
Pre-orders for the Amazon.com exclusive Chibi-Robo amiibo has yet to sell out four days after it was released. That outcome surprised some collectors who predicted that amiibo would sell out in less than a day. Here's what Amazon.com had to say about that product via an email:
"Purchases are limited to 2 per customer," Amazon.com said. "We have ample quantities of the amiibo, but do expect to sell out. Please act quickly Thursday afternoon for your best chance at buying the character you want. Demand is expected to be very high, and there's no guarantee that it will remain in stock for long."
Demand for that exclusive amiibo is low mainly because it's readily available to the masses online; as a comparison, demand for exclusive in store amibbos are high because they're scattered throughout thousands of stores.