I don't want to create problems to anyone, so i will not tell you what is the skill but...
on Italian Amazon Skill Store there is at least one skill that has a Premium version. It is possible to buy the Premium "addins" via the echo device, and the alexa app, when you ask for the Premium version, shows the never-ending text of Amazon Terms . It seems all "original" and working.
What i am missing ? Maybe there is a beta invitation-only phase of In-Skill Purchasing, here in Italy ?
Thanks, ciao !