You think that's bad? Grugnar charge 80% to sell rocks in front of cave, but Grugnar killed by Bugluk and then cave belong to Bugluk. Bugluk eat you and take rocks if you try sell in front of cave.
In your cavemen logic the closest example would be that nobody killed the first guy; he was forced out of business because a new cave opened nearby and they were selling rocks much cheaper.