For 700 sqft, I doubt you would need a 30K btu stove, maybe only half that if it is reasonably insulated. So the usage would be half also. 60 gallons per month.
Wood depends on so many things. If you have your own and cut and split it, etc., it is the cheapest not counting your time. If you buy it ready to burn (after some more seasoning usually) it costs a lot more.
Here is a neat fuel cost comparison calculator someone posted in another thread about firewood: Fuel Cost Comparison Calculator
Hey thanks for that I will mess around with it see what it has to say!! I don't have my own wood supply any longer and we were hoping to get rid of some of the mess with wood!! I would rather spend my time flying kites than splitting wood truth be known!!