Of course nothing is free. That is why prime members are paying $79 a year for the upgrade from free supersaver to free 2 day shipping.
The real issue here is that amazon is accepting the $79 fee, but not passing any of it to their third party retailers, whose offers are still labelled as "prime" (when they are not).
The real issue here is that amazon is accepting the $79 fee, but not passing any of it to their third party retailers, whose offers are still labelled as "prime" (when they are not).