Here it would be 1.000.000.000,00 (or you could drop the dots, too)
Some people incorrectly (the Finnish standard is for separating decimals is using comma) use the dot for the decimals, I guess that's mostly because they've used calculators at school and at work. Why on earth aren't calculators localised? They've never been.
KaeptnOvi's system is good, since you can't mistake the 's and ,s for each other.