I prefer to buy it by the cord (Or ton) and the thousand, leaving room in the contract for increasing the harvest numbers
(I always estimate low to be certain I can meet the goals I set for $$ for the owner)
and for stopping until market conditions come back around should they go flat. Pay weekly, supplying the mill slips with payment for same. It's the only way to cover your butt.
Buying the whole tract via sealed bid might be OK, but you better be danged sure of what you will be getting for volume and grade...if every other tree has rot or bugs and you didn't account for that....could be bad times.