My youngest son was/is a collector. He is now selling his rarest cards on eBay. He has kept them in "gem mint" condition, and sends them off to an independent rater to get that appellation applied before he puts them up on the bay. He has had several cards that have gone for hundreds of dollars. I think the best one so far was about $650 or so. He has others he has yet to sell that are similarly priced.
"We are not provided with wisdom, we must discover it for ourselves, after a journey through the wilderness which no one else can take for us, an effort which no one can spare us, for our wisdom is the point of view from which we come at last to regard the world." --M. Proust