Living in Japan, I became accustomed to using numbers for up to around 10,000 yen ($100USD) due to interactions at the stores and around town, but when I would hear the price of a car (1,000,000+ yen or 100 myriad yen) or a house, it would just confuse me and not register at all. It’s all just based on your personal experience, I think.
I have the same experience with German reversed way of speaking numerals, yet I speak the language fluently, including a good understanding of Swiss German as well.
But reversing back the numbers into my Portuguese brain, just doesn't work after a certain size.
There is (for me at least) something very deep (in the brain) regarding numerals and basic math.
I am quite proficient in English, but always do arithmetic in my native Bulgarian and then have to translate the result (unlike other speech, which flows freely).
And not for the lack of trying.
And that is even though Bulgarian numerals do translate 1:1 to English.
I read a fascinating article once I've never been able to find again that said the brain actually has internal biological representations of zero and one along with a rudimentary representation of two, but nothing above that.
