Because the alternative is starvation. It's not like great food is available for much of the winter in many places. If you couldn't eat the somewhat rotten pie, you didn't eat.

So in that situation trade the costly spices for ten non-rotten pies, is my point.

There aren't ten non-rotten pies available. As winter progresses, almost all the food is getting progressively more rotten.

This story is of a Norwegian ship, a place where they regularly ate fish soaked in lye. Their food options weren't great.

Yes, I give up, you are right. As winter progresses in Norway, everything starts to go off in the heat and the only way to avoid starvation is to season the rapidly decomposing food supply with spices worth more than their weight in gold. I withdraw my erroneous comment.

"Spices can also exert antimicrobial activity in two ways: by preventing the growth of spoilage microorganisms (food preservation), and by inhibiting/regulating the growth of those pathogenic (food safety; Tajkarimi et al., 2010)"

Food can decompose even in the winter, but you likely knew that already given your sarcastic reply.

People don’t make a bunch pies in fall and then store them for winter. They’ll store rawer ingredients, like flour, live animals or dried and pickled veggies and meats that don’t perish as easily.

People would often make a pot pie, which got it's name from literally being the pot they cooked the food in. Everyday they'd remove the top, add more ingredients, and cook it again.

I'm unsure of which regions did this, but I didn't mean they baked a bunch of pies in the fall.

Also known as a perpetual stew: https://en.wikipedia.org/wiki/Perpetual_stew