Next cheapest price is $449 according to priceme.
https://www.priceme.co.nz/GoPro-Hero-4-Black-Edition/p-89085…
The HERO4 Black has improved image quality, a 2x more powerful processor with 2x faster frame rates than previous models to enable to you to get immersive images of you and your adventures in high resolution photos and high frame rate video. New Protune™ settings for both photo and video allows you to control colour, ISO limit, exposure and more. Other features include improved camera control, selectable field of view, night and night lapse modes and a new HighLight Tag to mark key moments. This camera takes performance to a whole new level.
The Hero4 Black is very capable. Doesn't have the built in touch screen of the Hero4 silver.
The Hero5 image wise is very similar to the 4 black, just the 5 gains a waterproof body, better audio, a touch screen, stabilisation, voice controls etc.