It's not really that far off the mark when you just look at your own budget at home, though. Shit on average costs about 10-20% more (and for some products, even higher than that) than it did 5 years ago. Hell, 85/15 ground beef was ~$5/lb back in 2019/2020 where I live, now it's $7.50/lb, that's 50% increase right there. Same with milk and eggs.
Bottom line: I think you way over analyzed something that can easily be solved by just looking at your grocery and monthly bills now vs a few years ago.
Their estimate of $11k is too high for me. But I can easily see this being the case in some areas. For me, our cost of living has definitely increased by about $500/month, so $6000/yr. But, I also live somewhere with a relatively low cost of living.