I know that Prime Video has either rentals and purchase to own (regardless, the ones with higher resolution costs more when speaking about one time purchase rather than rentals). I’ve managed to purchase The Unit (All 4 Seasons) for about ¥4000 in total (or about ¥1000 per season in HD) on Prime Video (Japan). Rentals only last 48 hours while purchases are intended for lifetime streaming without an expiry date.


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: https://www.primevideo.com/help?nodeId=G4HUP5EWXFZDHGFC