There have been multiple sold auctions on eBay recently for this item, you can check on there.
Thanks and yes, naturally, I have checked ebay. The 2 auctions that show up (as sold) were listed by the same seller and claim the buttons were owned by an "early TSR employee." Although unnamed, I was thinking that the mere mention of a TSR provenance might have inflated how these are valued. Plus ebay is nuts with prices. I thought buttons like these have likely migrated into a number of collections owned by folks here and that somebody might have a better sense of what this button is worth (although I am not looking to sell). I'm all for the free market, but I like to have a realistic sense of value for the things I have added to my own collection. I paid $35 for this one - assuming ebay is a bit high....maybe $50 is a good ballpark $$.