It depends on what you are planning to use it for.
If you want to take professional, TV-grade footage, then the GoPro Hero Black 4k may be your best option. However, these go well for around $500US.
The quality of these (and especially the low-light quality which had been an issue on the GoPros) is incredible. Here you have a camera that delivers really everything you could possibly expect from high-end power gear. One needs to remember however that in order to properly use this kind of footage, an adequate computer is needed. 4k is very high quality and high resolution and not all computers can render/edit, not to mention play it.
So unless you have the gear to handle such mega HD resolutions and only want to get good home-video or action footage for your personal consumption, this may not be a worthy option.
On the other side of the spectrum are the likes of the SJ4000 Chinese GoPro clones (read: knockoffs) that carry a pricetag of around $30US.
These come with HD video that indeed rivals the lower-end GoPros in quality. These kind of cheap cameras are good enough for HD home videos, or throw-away cameras for your next bike-stunt. The 4k versions of these that usually don't exceed $100US or less even come close to the GoPro Hero originals.
Within the range of these two examples are various other makes and models, both from GoPro, as well as their rivals and imitators. So unless you are very serious about the quality of your footage, buying a high-end (or even low-end) GoPro may not be necessary in light of the cheaper and equally capable variations.