Binder pages for slabbed cards
 

If the eBay seller is a member here, I apologize. However, charging $50 for a single Ultra Pro page is beyond outrageous.

At first, I thought this was just a market value gone completely out of control.
Nope, I was wrong. The very next listing is someone selling a full box for $75.

One is PSA, one is BVG.

These were on the market for about ten seconds and consisted of a clamshell rigid plastic structure. Didn't do well but have become very popular in recent years as the only really good product for putting slabbed cards into binders.

Looks like there is a new company making similar products now