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.