ENEngadget
You'll now have to fork out for an additional subscription if you want to watch 4K content on Prime Video
Amazon is implementing a new subscription tier for Prime Video called Prime Video Ultra, which will cost an additional $5 per month and is required for 4K UHD streaming. This change removes 4K content from the standard Prime membership, which already costs $15 per month. The new tier also increases download capacity and concurrent streams, and includes Dolby Vision and Dolby Atmos support.