This is an Amazon add-on item (to get it, you need to order $25 worth of other things). Looks like they're limiting orders to five 24-can cases for this go-round. Based on my Camel alerts, this is price drop seems to happen about once a week for a few hours before returning to $9.50 or thereabouts.
As some here may know from previous pet food threads, I usually jump on these deals every few months to donate to my local no-kill shelter. I encourage you to do the same.