The problem with pricing by volume is that the average consumer can't really manage their volume.

Would the consumer be responsible for paying for: -DDOS (not only can you knock them offline, you can cost them big money) -Spam (Both received and botnet sent) -Retransmissions for traffic the ISP dropped due to congestion -Ads (adblockers could reduce bandwidth costs by a third)

I personally would love volume pricing. But I also would not want to provide tech support next time my parents get hit by malware and get hit with a $1000 isp bill.