No, 2,50€ is 2€ and 50ct, 2.50€ is wrong in this system. 2,500€ is also wrong (for currency, where you only care for two digits after the comma), 2.500€ is 2500€
what if you are displaying a live bill for a service billed monthly, like bandwidth, and are charged one pence/cent/(whatever eutopes hundredth is called) per gigabyte if you use a few megabytes the bill is less than a hundredth but still exists.
We (in Europe) probably should be thankful that you are not using feet as thousands-separator over there in the USA... Or maybe separate after each 2nd digit, because why not... ;)
It makes sense from typographical standpoint, the comma is the larger symbol and thus harder to overlook, especially in small fonts or messy handwriting
But from a grammatical sense it’s the opposite. In a sentence, a comma is a short pause, while a period is a hard stop. That means it makes far more sense for the comma to be the thousands separator and the period to be the stop between integer and fraction.
I have no strong preference either way. I think both are valid and sensible systems, and it's only confusing because of competing standards. I think over long enough time, due to the internet, the period as the decimal separator will prevail, but it's gonna happen normally, it's not something we can force. Many young people I know already use it that way here in Germany