How can I change the structure of the last sentence?
Ultimately, Spam is facilitated by the low cost of interruption. Unlike written mail and phone calls of the past, there is no postage or per-minute cost. Because Internet access is billed by the month or the data pipe rather than the message, email can be replicated and broadcast to millions of addresses without marginal cost.
I understand the main idea of the sentence but I can't get the part "or the data pipe rather than the message."