In short, I see no economic basis for such metering, and no moves towards such metering. Maybe I'm wrong, but I doubt that we're going to see any change in this any time soon.
There is another reason why some people don't like metering - it makes predicting costs much more difficult. Imagine your local library or university dept trying to budget for internet access. I think I saw a comment that half the cost of a long distance call was collecting the data and processing the billing. Can anybody verify that?
I think it's a North American view of the world, unsurprising on NANOG :-) Traffic metering is the dominant charging mechanism for permanent connections in Oz and Connect differentiate traffic based on its source (domestic/cache/external).
How much trouble is it to collect the billing data? What are the relative rates for domestic/cache/external?