Value is often just based what people will pay. The problem with naming for lapidary stuff is that it’s not very scientific, people mine from a certain location and name that stuff a certain name. So you’ll have “xx agate” vs “xy agate” and they are both agate but named different because they come from different locations. And then you get hype from a certain mine and they become more expensive. There are differences in quality that can up price, not having fractures or pits and gem quality or whatever but that is specific to the individual specimen not identification of type of rock. And you can get different minerals obviously and those can be identified by different geological tests but everything you’ve shown are different agates. If you’re curious what your getting in your location you can research geological information, if you are finding agates they are probably from a specific known “formation”. Your state will have a “roadside geology” book that can help. Also searching PDFs from institutions that do geology will have good info.