There is a whole industry based on this kind of reasoning - it is called marketing. How much saving is attractive enough? Often people buy products "on sale" and end up spending more (e.g. there is a cheaper option available, buying a larger format would be a better deal, etc.)
So, how come marketing does exist if we are aware of these tricks? Because nobody thinks about the consequences.
If you were to ask Joe today to trust you to go to Uruguay and bring back $1000, what would Joe say?
a) Sure, I'd save $200 ---> might end up losing $1000
B) No way, lesson learned ---> "not all expats are the same" ---> won't save $200, but won't lose a dime
There is a 50/50 possibility that Joe gets scammed again. Either he gets scammed or not. By suggesting that "most of the people are not scammer" you no longer feel it's 50/50, maybe a 90/10, so you'd still go for it.