Do not “buy” from these places. They don’t even own the content they are selling. Your access to the show is contingent upon Amazon Prime Video continuing to have license agreements with the owner of the content. As soon as their (separate) deal with the company that owns the content expires (and it will eventually), you will lose access to that content.

From here: www.primevideo.com/help?nodeId=G4HUP5EWXFZDHGFC

On the title’s product page, you’re shown available purchase options. Note: Buying a title adds it to My Stuff and will generally be available to you for download or streaming, but may become unavailable due to licensing restrictions or for other limited reasons; renting a title will add it there for a limited period. Rented titles stay in your video library for 30-days from the date of the rental. However, once you press play on the rented title, you have at minimum 48-hours to finish watching it. Some titles have longer viewing periods.