I have been getting pans off ebay that are fully gloss black shiny smooth inside. Like you said, the real deal seasoning. That comes with years of cooking in it. That kind of coating isn't something we can rub on and heat in the oven and it's done. Frying and cooking greasy foods at high temps build that black seasoning.
For collectors, they want to see the metal. They like them cleaned and oiled. Lots of sellers on ebay claim their pan is cleaned and "seasoned" when in fact it is only cleaned and OILED. Fortunately for us who buy them to cook in, a seasoned and black skillet with years and years of use on it won't fetch collector prices and can usually be bought cheaper. I would pay extra for a pan that is already shiny black inside as opposed to how clean it is.