V-Mail

>I can't even imagine the overhead of unpacking and then "scanning" each of those letters by hand

At this point in the war, all mail (not just those to service members) entering and exiting the United States were opened by hand and microfilmed for censorship and counter-espionage purposes by the Office of Censorship[0].

So technically the mail opening and scanning aren't extra overheads, since those same steps apply to regular snail mail as well.

[0] https://en.wikipedia.org/wiki/Office_of_Censorship

The post office had bazillions of employees and alot of cash.

My dad used to write letters and QSL cards to people all over the world in the 60s/70s. He recalled that frequently letters to soviet bloc states, northern ireland, and some african countries were opened, either by the US or other country.

I was confused by this also, especially since it seems unlikely to be able to locally procure paper in the middle of a warzone. However I do think it probably.makes logistical sense since you can pre-stock the paper (e.g. on a ship) or ship it with a much higher-latency mode of transportation (e.g. ocean freight).

The paper could be sent in bulk from wherever it could be sourced from, including non belligerent countries, it also could be shipped in large rolls instead of harder to handle mail bags, it also reduced the need for inbound sorting too.

The point was not to save paper, it was to avoid sending all that paper back to the US.