Our Central Boiler was about $7,000 installed, with parts and slab (did our own labor). The house is a little under 2,000 sq ft and heated with hydronic floor loops. There are a lot of windows and skylights and lofted ceilings. Lots of heat loss here. We were told that we would burn about 5 cords a year. Maybe with a mild winter year and all oak we could just get by with that with the temp set at 68. We set the temp at 70 though, and burn more like 7 to 8 cords of mixes species a year. I would guess that in Maine you will burn over 10 cords in an OWB, maybe as much as 15. Depends on age of your house, the layout, and quality/quantity of insulation. Also window area, and if kids and wife keeps the doors closed, elevation, sun exposure, snow build up, etc.
If I had it all to do again, I would do what we did all over again. No regrets here. The OWB burns a lot of wood, but it grows on trees, and we have over 80 acres of trees here. It works well with the existing heating systems (solar DHW and hydronic flooring heated with flat plate heat exchangers). There is usually more windthrow than we can burn here, really. And if not, there are dozens of slash piles to raid within a few miles of here (we are deep in timber country). We also set our OWB less than 10 feet from the carport at the side of the house. There is a draw behind the house, and the smoke flows down that 90% of the time. Smoke has been a complete non-issue for us with the OWB. I would think before putting the OWB as far as 100 ft from the house. You have to fill it twice a day. Maybe build test fires and see whare the smoke drifts naturally at different locations. You may be surprised where it drifts.