Posted By:
Trevor HockingWhat a great question. I personal collect display items as well. I think why most larger photographic items are less expensive than there "card" counterparts is size. Most people don't have the wall space or want to give up the wall space for display items. Also it is a lot tougher to secure items on your wall from theft or your child's sticky fingered "friends". 
Also most people do not have the knowledge when it comes to photographic items to buy with full confidence. And finally they are so rare and hard to find they never come up for auction and when they do most people pass because of all the above. By the way SHHHH this is the only area in vintage baseball I can still find great bargains. 
Trevor