I was thinking of getting one as a folly for my garden until I found out the prices. It seems that there are many different ones some of which are highly collectible. I knew a man who had 3 in his yard and bearing in mind that they are cast iron and very heavy and expensive to transport I offered him £500 for one thinking he would jump at it. No he said they have to be about £2000 each but you can have one for £1500. Too much I said but when I started looking into it it was not.
It is one of those odd things that you never really think about unless you have a sudden whim for a new garden ornament but when I looked into it was very interesting learning about all the different types and ages or do I need medical help :-))
I did not get one in the end due to the cost and difficulties involved in transporting it and situating it in the required position ( more complicated than one may think)
Back to your point, it is to my mind a shame to see these traditional things vanishing, I suppose it won't be very long before we have plastic post boxes.