You don't know how DDoS works. The coffee machine might only have to send one packet per minute. The combined force of 100 million coffee machines distributed

You don't know how DDoS works. The coffee machine might only have to send one packet per minute. The combined force of 100 million coffee machines distributed around the globe sending 1 packet per minute each to the same destination means that, in your suggested model, the end user traffic sources barely incur cost at all, while the target and every unrelated third party who happens to be unfortunate enough to be "close" to them are bankrupted. Congratulations, you've just turned a temporary network DDoS into a permanent financial one.