I agree to some degree with some of the posters in here, you do get what you pay for, but Go-Pro are vastly over priced, and I think you pay for much more than you get. Sure you get a good bit of kit but there are alternatives that offer OK resolution. Do we need 4K? that is very high resolution, most of us will watch our clips either on out computer or big TV screens, 4K is not necessary and you probably would not notice the difference even if it was projected onto a 15 foot screen.
I have a Go-Pro Hero 3 Silver it has the top resolution of 1080P, then 960 then 720 and lowest resolution of WVGA which is not worth even contemplating using.
I have I had it for about 3 maybe 4 years now, I paid about £360 for it when it was new, I do most of my riding filming in 920 or 710
But to be honest the finished clip is hardly any better that some of the action cams on sale in FleaBay for around £45.
Ok sure there will be no support of service with the cheap intimations but if it lasts just one year then its only cost you less that £1 a week, about that the price of a packet of chewing gum.
Don't get me wrong Go Pro are good, I had an issue with mine when it was about 2 maybe 2.5 years old and 18 months out of guarantee I contacted Go Pro and told them about the problem, I posted it off the the Netherlands at their request for repairs and two weeks later I received a free brand new unit compliments of Go Pro. You will not get better service anywhere than that.
Would I but Go-Pro again? you would think so, but I'm afraid I wouldn't, I believe they are probably the best but they have priced themselves out of the market for me.
The Hero Black is now a quid short of £400, you might get it for £300 if you shop around.
When I replace mine I am going down the Fleabay £45 route.
Most technology in the last few years has dropped drastically in price but I am afraid Go Pro are the same price now as they were 5 years ago, and 720 or 960 resolution is plenty good enough for home video clips.
Go to bike meets and ask the bikers who use cams what they think of the unit they are using.
Oh! one other thing is that I use my Hero 3 for snorkeling in Crete and it is waterproof to 40 meters, some of the cheaper ones are just splash/rainproof.