I am not sure why I have to pay for "data" at all. Surely ISP's do not buy "data" blocks from the wholesaler and resell them to me - they buy bandwidth, right?  In that case, what I want is to purchase a share of their available bandwidth.

If I buy 256 kb/s of bandwidth that effectively limits the amount I can download in any given time period.  If I want 2mb/s that increases the amount of data that I can download by virtue of the time it takes to get the data throught the wider pipe. But if I want a good fast connection (say 10mb/s like Mauricio - lucky man) then I need to pay more, but I have access to a larger data package because the pipe is wider.

From my perspective, the only justifiable charging scheme is - by bandwidth - because that is what the wholesaler is payiing for and it distributes the cost of service provision according to who is using the service.  Its all about bandwidth at the end of the day.

Cheers Mike