After some research I learned that the Amazon had got the patent for this device (9,013,416) (
http://portal.uspto.gov/pair/PublicPair), and also is paying the fees to keep the patent valid (
https://fees.uspto.gov/MaintenanceFe...Number=9013416).
However, it does not produce anything specified in the patent, and thus creates an obstacle for others willing to produce it at a reasonable price FOR YEARS AND YEARS. And obviously Amazon does not give away its patent for free.
This approach reminds of a dog in the manger which will neither eat himself nor let the horse eat.