Really hard to get a real answer out of this. I burn 18ish cord a year to heat our large house, shop and farm stand plus a couple cord to my mothers house. But I’m not paying anything to do that beyond fuel. None of the equipment besides the wood splitter (which we built anyways) is solely for wood. So it’s essentially free heat over running oil (which we do still burn a little bit of)

But depending on your situation wood might not be the cheapest. For example you could be using one of the new junk EPA stoves that requires 16” kiln dried wood that you’ll pay out the asshole for, in that case fossil fuels might be more cost effective.