How much should I sell my GoPro Hero 4 Black for?

I'm selling my GoPro Hero 4 Black to get a DSLR. I've used my GoPro probably 15 times and there aren't any scratches/smudges to be found. You really couldn't even tell that I ever used it. I also have 3 batteries, a dual charger, a chest mount, a floating handle, 32GB SD card, the curved/flat adhesive mounts, and everything else that came in the original box (including the manual). Do you think $500 is a reasonable price?

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