This is increasingly common, and part of the problem is that Facebook is slow to crack down on fake accounts. We may be surprised that an image from Kasier's Bunker is on Facebook, but we have to accept that there are still a lot of collectors who have never heard of the site, just as many collectors don't know about the large shows like Show Of Shows.
These scammers aren't just hitting militaria groups, it is widespread across the commerce sections of social media.
However, the larger problem is that PayPal employs a "Friends/Family" method to send money. That should be completely banned, as it makes it all too easy for scammers. I know some people will disagree with me on that point, as no one likes fees - but consider it the cost of doing business. If you're selling an item, pad the 4% fee into the price. No one SHOULD EVER buy goods and use friends/family, as it actually is in violation of the terms of agreement.
I fell victim to a scam, and it happened ONLY because PayPal allowed friends/family to be the default for the "seller." I am normally extremely careful, but I was distracted when I paid for the item and didn't realize until I hit send.
I have tried to ask PayPal why users can't simply turn it off entirely, and I wasn't given a straight answer. The reason is that they don't care.