FWIW I used to order kitty litter on Prime. Free shipping and all that. Turns out they hugely marked up the retail price for the free shipping. I’ve since found it on Walmart’s website for about 40% cheaper. Free shipping if I order 5 at a time.
This is really common on Amazon, even for things that aren't heavy/large. Amazon used to be a place that gave you some of the best prices on things, but that hasn't been true for a long time.
Oftentimes I would have been overpaying 20-50%, especially on small, <=$15 items.
It seems like something for $11 is a good deal, until you can get 3 on eBay for $8.
I wouldn't want to be the delivery guy who has to bring that to your door...