Silly preview function!
I understand that materials, printing and distribution are not Significant portions of the cost. But they are A portion. If Amazon is selling an e-book for more than the MMPB, as they seem to be doing in many cases, all I can infer from that as the consumer is that they're greedy.
Even if it costs 25 cents to print and distribute an individual book, I'd expect that the e-book would be at least 12 cents cheaper than the paperback. On a $7 book, if $0.25 was hardcopy costs, it is a negligible cost but still a discount I as the consumer would expect to see some portion there of.