What is it really worth??

I?ve been collecting for several years now and do not consider myself an expert by any means; however, I have noticed that pricing discrepancies are the biggest thorn in my side. I enjoy collecting for the historic value more then anything else, but lets face it, we all what to know what our coins are ?actually? worth. I noticed that the discrepancies between NumisMedia, PCGS, Whitman?s, Coin Values, and others are sometimes vast. Why is this? And will I ever know what my coins are really worth? I understand that value is sometimes in the eye of the beholder, but the wide range of values assigned to coins is sometimes confusing. I usually attempt to gain several quotes and work out an average. Does anyone have any suggestions?