>For how much (in USD$) ?

Its equivalent would be about 35.00$ to 38.00$ US approx.

>My point consist basically, to compare the ADSL in different countries.. So, taking as example 512k (not corporative) costing USD$ 21 in Brazil.. How much, do you think it will be, there in Canada ?

I don't have the exact rates for ADSL in Montreal from various ISPs as I never use that type of connection. All I know is from what I hear.