What do you consider big? $4 is a loss of 13.8% of the sales price. If you assume he already has some costs (his time to write the book is quite valuable), the loss in profit is even more.

A 13.8% loss in profit would sink many businesses.

Plus shipping costs. That print on demand price sounds good, where did you find it?

I will gladly pay shipping costs when I buy a book. I just googled "price for print on demand paperback"

Createspace has great pricing. I'm guessing that was the source.

After shipping, it costs me about $3/book for a 160 page paperback copy of my book if I order 20+ at a time via CreateSpace.