It seems to me that the dollar value of their marbles is why folks inquire here. Marbles look so cool, organized and sorted, or just in a big circle. They look valuable! How can they not be? Especially if they are from an old collection. I actually thought mine were not worth much of anything, in spite of my brother saying that some had some value. I was completely correct!! And if I had kids to give them to, I would. I actually tried but those kids are from a family of collectors and did not want take them away from me, because of the sentimental value they had! "We can't take those! Those are yours!", they said enthusiastically! It was a very surprising and wonderful response by them. They would only trade!
I've wandered off. I support your statements as to the value of marbles in question, these or others. Typed responses may seen short or dismissive, that is their root failing. It takes a lot of effort to type something that doesn't sound that way...look at me here!! And I am still not sure I got my ideas out the best way!