"Mille" means a thousand and "milione" means a million. It just so happens that English may use a different number than Italian to express something.
Mastering a foreign language means speaking it idiomatically correct, that is by using stock phrases and images that are used in the foreign language and that may be different from those used in one's own language.
Where English has "That was the straw that broke the camel's back, in Danish we say "That was the drop that made the cup run over" (Det var dråben, der fik bægeret til at flyde over").
And that in Italian is "è stata la goccia che ha fatto traboccare il vaso" (http://www.idiomtranslator.com/IT/frase/2049/la+goccia+che+ha+fatto+traboccare+il+vaso) :)