I bought the one pictured in that YouTube video right before Christmas. I didn't think to ask how much it was; I assumed it was around $150. The SA who rang it up had to search for its price info in a binder he had by the register. When he finally found the info, I was shocked to discover it was over $300. I bought it but returned it the next day after I realized I wasn't recovering from the sticker shock. I also didn't love it on my pochette.
I don't use the chain on my mini pochette, so I used a pair of needle-nosed pliers to remove the link attached to one end. Then I doubled up the chain and attached it to the end of the little carabiner clip on the other end. It works perfectly as a pochette extender! The one I returned was much longer than what I wanted, and both clips at either end were much larger than the clip on my pochette. The clips' bulkiness really bothered me and looked out of proportion with my pochette.