For a tree service, its and add on, get paid twice for the same product, although there is still the processing. For an individual buying log length cords, processing,selling & delivering,very slim profit. Mulch is another good area for tree service,just have to offset cost of tub grinder ( contracted , rent/lease, purchase). Also has a wider application without as much concern on bug transport or the inevitable quantity/quality complaints of firewood sales. Personally I do not sell firewood except for a occasional face cord, and I can count those on one hand over a 10 year span.