You can buy cheaper action cameras, but they won't offer all the features of our top picks, and likely aren't as durable. Typically they have lower build quality, inferior lenses, no waterproof ratings, and crappy chipsets and specs. Still, depending on your needs, something like the Dragon Touch ($70) might be good enough. The results won't be GoPro-caliber, but if you're just getting into action cams, this is a good way to test the waters.
Readers often ask, why spend $400 on a GoPro when they can get a camera with 4K video for $100? It's a fair question, and the answer comes down to software, primarily image stabilization. Action cameras are intended to be strapped to helmets or clipped to your chest while you skydive, rock climb, and race through the city on a scooter. Without stabilization, the results are something even your closest friends won't sit through. So yes, you'll get 4K footage with the cheaper cams, but it'll be footage no one wants to see. In our view, you're better off spending another $100 for GoPro Hero 9.