Actually, the idea of charging for email has been around for quite some time. Remember that spam works because it is free. Hardly anyone actually buys anything from spammers but they send out so much of the stuff that they get quite a few customers anyway.
Now, if they had to pay a penny to get through a block like that, they would never send another spam out again. They would probably send email out to the people who had already bought stuff from them because there would be some chance of getting money back but to ten million random addresses? I don't think that anyone is going to spend a hundred thousand dollars to send email to the 9,999,000 people who will never respond.
Of course there is going to be a problem with legit operations like listservers but that can be taken care of with some type of friend list. Hopefully one that is customer controlled.