Lightning Source is the dominant Print-On-Demand company, producing books for publishers of all types and sizes, including my own Silver Sands Books.
Their printing price for standard paperback books is 90 cents, plus $.013 per page. A 300-pager will cost $4.80. Pricing-per-page seems very logical to me, but that's not the way some self-publishing companies work.
Here's the price chart form E-BookTime.com: