Super fascinating conversation here! I didn't know about postcards being charged by the word in the past - I'm thinking now about our collection of old family postcards, mostly accumulated by my great-grandfather, born 1899. From what I can tell, he was given a fancy postcard as a school prize for good attendance when he was five years old, and collected postcards all his life afterward - when his father spent four years slogging around Europe during WWI, he made a point of buying as many different postcards as he could source and sending them home for his son's collection. He doesn't seem to have worried about paying by the word, though, as he wrote all over them, little notes and letters to his son, sometimes continuing over several cards (but I think my great-granddad disposed of any duplicates, so we don't have the complete set of messages, only the unique cards). So it's fascinating to look on that correspondence in light of the charges - but I think the postcards must have been put into envelopes with letters to the wife, since none are addressed or stamped. So there'd have been a letter to the wife, with the postcards included for the boy - and he apologises in several of them for not managing to find new pictures, so he was clearly always on the look-out for cards to join the collection.
This contrasts with other family postcards in the collection that do seem to have been concerned with being charged by the word, being very conside - one that reads, "we are home mother", being case in point!
_________________The Life and Times of Me"Real life is an illusion, albeit a very persistent one" ~ Albert Einstein