I know it is sarcastic but there is a website where you can calculate how much it would cost to heat with dollar bills.
https://coalpail.com/fuel-comparison-calculator-home-heating
https://coalpail.com/fuel-comparison-calculator-home-heating
You can maybe push it down to $300/cord if you know a guy, but then you're not getting properly seasoned stuff, you're getting stuff recently cut from a dead tree left standing for a few years.