To add to the complexity of the whole situation, some countries don't separate by thousands (every three zeroes). India uses a 2,2,3 system (crore, lakh, thousand).
Petrol stations... I have no idea how widespread this practice is, but at least in Germany fuel prices have 3 decimal points to better confuse motorists. The third number is usually displayed smaller and is of course always a nine. So, if you see the price for a litre of diesel at e.g. 1.62⁹ €, you might forget to round it up mentally.
Dot is often used as thousands separator too.
I remember the first time I saw 10,000 as a price and thought: 10 bucks? So cheap. But also: who needs 3 decimal points for a price?
Looks like its more or less 50% of the world [0].
[0]: https://en.wikipedia.org/wiki/Decimal_separator#Conventions_...