No, definitely not free - US $25. You can easily get smart plugs that work with Alexa, GA, HomeKit, IFTTT, Stringify, and whatever for the same price or less. I honestly don’t see any reason to buy Amazon’s smart plug.
I bought this one Amazon Smart Plug, works with Alexa https://www.amazon.com/dp/B01MZEEFNX/ref=cm_sw_r_cp_apa_i_oQfPCbF51GAZK
But be aware there are others that come in a 4 pack for like 36 bucks