Toilet paper.
Costco's price hasn't appeared to rise, but my local supermarket sure has. The 12-double-roll pack I would buy pre=2020 at publix, their own brand, was around $7.50. They are now charging $11.79.
Meanwhile the Costco Kirkland pack is 30 rolls for about $20 in store. I got a pack of it for my stockpile and went thru it recently, but then went pack to Publix... and boy, not just the sticker shock - the Costco sheets were bigger and softer, the overall square footage of their pack 1429 to Publix 428, so the price becomes very clear. Now I just have to figure out better ways to store it...