cheapest firewood
For just straight buying...there were few families near to me in maine that just bought an entire tractor trailer load of logs every year, then cut them up and split and stacked right there in the yard where they rolled the logs off. It was wicked cheap to get wood that way.
Anyway, most folks don't need that much wood, but just buying long logs delivered then doing the work yourself, the "processing", is an option most folks don't think about. Then you don't need a big hauler or go travel, etc, no need to beat on your ride or buy more ride than you need, but you can still have a lot of chainsawing fun and splitting fun and save on the heat bill.
Like a lot of guys have said, trees are almost free, it's the felling, cutting to size, splitting and delivering you are paying for.
Eliminate some of those steps, it gets cheaper real fast.