From my own experience I'd say that your figures are very close. I used to use 600 gal. of propane or maybe a little bit more each year. The last two years I've used a little less than 100 gal. of propane a year. That's for cooking and a little bit of heating.
I haven't kept real close track but I'm pretty sure that I've never burned three cords of wood in one winter. I've got my wood stacked so I can tell how much wood I'll use this heating season.
I've spent $850.00 on saws and a little bit more on gas and oil this year but I'll save more than that this winter. There shouldn't be anywhere near that much cost next year (unless I buy a 346 ) because I've got almost four years of wood stocked. I'm going to try and stay at least four years ahead because I have room for at least three years under roof.
Dan, there is something else about propane. Many people don't really understand it. That stuff can be dangerous--perhaps far more dangerous than natural gas. I watched a massive propane leak at a major building "fry" several people trying to control it. Propane is invisible and hovers on the ground. One spark can set it off like a pool of energy, and you may not even know it is there waiting for a small flame.
I've never seen firewood do anything quite so destructive that I have already seen propane accomplish. :censored: