but now if we start this there are many types of bandwidth from cogent bandwidth to level 3
Yes but I did say "quality" not cheap.
I would say that the general standard would be $1.00. Slightly lower is fine of course, but too low, and then you're taking un-needed chances.
Just remember, that price is not the only factor of choosing a host, and the higher the quality of the bandwidth, the higher the rate will be.
It all comes down to...settling for the lowest price, or paying for quality...or in better terms..it comes down to how much you care about your website.