Paying for wood, labor, fuel, wear and tear on equipment, rent, taxes, utilities, advertising, etc, etc, etc... everything from pens to toilet paper.
No right or wrong answer in a business per say, but a good idea is to charge as much as the market will support. There will always been some "beer money" sellers here and there, but it's one thing to sell a few cords a year for beer vs if you don't sell wood, you go broke and close the shop doors.
Personally I wouldn't mess with delivery of 1/3 cords, but if that is what your market dictates, so be it. Here if they want small quantities like that, we either sell them bundles or loose wood that they load themselves. Have a 1 cord min on deliveries.
I stayed at the same price for 10 years, I decided I had to go up on my bagged wood at the first of the year. I was afraid it would hurt sales, and it has but only slightly. There buying only slightly less in volume, but at the higher price I'm actually making more money.