So of the two items you cherry-picked to support an assertion that groceries have more than doubled, one is up...around 30-35%. In fact, there doesn't appear to be a single food item in this list that has doubled in the past year. Eggs are the closest.
But that's not the whole story. Prices are not primarily set by wholesale costs for many goods.
I think cereal has only gone up 30%, although there have been other events that influenced Kellogs pricing (notice how the Poptarts boxes have changed slightly) and then there has been the opportunity to steal away some extra profit - https://www.wxyz.com/news/now-cereal-prices-are-on-the-rise-... (search for "Mills").
https://www.ams.usda.gov/mnreports/dywabutter_cme.pdf
https://www.globaldairytrade.info/en/product-results/butter/
But that's not the whole story. Prices are not primarily set by wholesale costs for many goods.
I think cereal has only gone up 30%, although there have been other events that influenced Kellogs pricing (notice how the Poptarts boxes have changed slightly) and then there has been the opportunity to steal away some extra profit - https://www.wxyz.com/news/now-cereal-prices-are-on-the-rise-... (search for "Mills").