comma or decimal point?

A confusing piece of French life to be aware of while doing number calculations or reading about numbers in the newspaper or in articles. In the States, if we were going to put something like it is 12.5 to indicate twelve and a half we would use a decimal point between the 2 and the 5. In France they would use a comma: 12,5. If we were going to say 12,000 people live in the town, we'd just use a comma. Here? 12.000 people. Random huh? Even more confusing when you get into things that we usually think of that have commas. Like: I had a budget of $45,000. Here? 45 000 $ yep, no comma or decimal point. I'm not sure how the rules apply across the board, I just know that it is confusing most of the time.