The nazis had a scheme to air drop fake notes into the UK during ww2, and I think the allies had similar schemes.

It’s not new, although I’m not familiar with anyone doing it with postage stamps.

Pratchett has done it though.

So am I the weird one for walking to my local post office and buying stamps directly from them when I need another roll? It’s not like the average person needs so many syamps that saving 50 cents per roll will matter much, and any legitimate source apart from the post office naturally has a markup in price.