RG8 is a class of cable that has nothing to do with attenuation, power rating, or material. It refers to the impedance and physical size regardless of what is stamped on the cable. RG8 is 50 Ohm cable that measures .405". The problem is that what materials are used and how it is made changes the electrical specifications of the cable.
Times Microwave makes an RG8 class and RG8X class cable. It is LMR400 and LMR240. Belden also makes RG8 and calls it 9913. RG213 and RG214 are both RG8 class cable as well. So not all RG8 is created equal. Some is much better than others. So it is stamped with a product designation other than its respected class to differentiate between one cable over another for the consumer to choose the correct cable for their particular usage. An example, standard RG8X has attenuation of 2.0 @30Mhz and Times Microwave RG8X (LMR240) is 1.3 @30Mhz.
It makes it difficult for people like me. I can (and have) research and know lots about coaxial cable and still have no idea of who is making it well and who isn't.
Experience trumps book knowledge. I have little experience with coax and only know of a few of the quality companies (Belden, Mil Spec, Times Microwave). Like you said, many lesser known companies sell China made cable that may carry the RG8 designation but be of inferior quality or it could be very old and outdated stock. It is that point alone why I am asking here. People have experience of what companies make quality and what to stay away from. The RG8U I found for $60/100' is made by Advanced Digital which is made in the USA. But I have never heard of them before. I checked them out and the picture of their plant looks less than sophisticated, not that what the plant looks like means much. It may be inferior quality, it may be good. It may just be a lesser known company that cant charge the premium prices. I just don't know. I should stick with a HAM supplier for my cable. That way I know I'm not getting old stock. I guess its worth the extra $20.