I hate to tell you ladies, but they really have no value at all in the antique or collectible market. They are worth whatever you can get for them on eBay or at a yard sale, that's all. The ones with silk buttonhole twist on them are worth more, only because the thread is not made any longer and it is great for embellishing, but it is the thread, not the spool that is sought after.
http://en.allexperts.com/q/Collectib...ead-spools.htm