Shamrock is right. They make money on the shipping and no it ain't a scam. I order lots of books for a penny but usually pay around 3/4 dollars on shipping so it ain't that cheap at all. It is very common to see books listed at $0.01 on amazon, half.com and ebay.
Lemme let you in on a little secret e-seller. The standard shipping is put up there because no seller knows who is going to buy the item and where they're located so they in effect, max it. They will cover themselves by using the excuse above: They don't know where the item is going so must cover the max shipping. They then send you the item and keep the profit (even if you are in the same state as them you pay 4-6 dollars in shipping for a small novel!).
The solution is something I have done once or twice (trust me it works if you have the nerve - which I do
). Check the postage cost on your received item stamped there by the post office. If it is lower than you paid then email the seller and inform him/her that you would like to be refunded the difference. Ignore any excuses about the envelope costing 3 dollars and suggest the seller buy them from their local Wal-mart at as low as 30 cents. If the seller refuses leave the details of paid cost and actual cost on their feedback and at the end add the word 'avoid'. That will make them think twice about doing it again.