The problem is, if you set the cost to be actual cost incurred, then anywhere remote or rural will be ridiculously expensive

Well I am not saying each letter, more that the system as a whole needs to be making profit in one area to carry the loss in another.. At this point we have way more places to deliver to than people sending regular mail.

I believe that every job should be sufficient for someone to live comfortably on

Looks like Canada post already pays the average or above average and is above living wage in most areas.

https://ca.indeed.com/cmp/Canada-Post/salaries

https://www.livingwage.ca/rates