While researching ancestors, I came across these books - Canadian Grocer. There are different years containing articles, ads and markets for different provinces. I found issues for years 1890 to 1922.
We had a small grocer at the end of the village where I grew up, and I used to go sometimes to get a couple of things for my mother. It seems to me everything was 25 cents? ... milk, bread, etc... I know that is just my childhood memories, I don't know how much it was, but 25 cents was a lot of money. My Mom also let me buy penny candy and I always got blackballs because you got THREE for a cent, not just 1. And each one lasted a long time.
Looking through these books you can see what your ancestors were buying and how much they might have paid for it.
Digging deeper, I found some similar for the US and for the UK.