Haven't been on in a few years and recently returning. No clue what a fair price would be or if there's a market for it. Do most people that would be able to use one just earn it themselves?

I'm not sure about price or demand. When the Battle Coliseum reopened in January after the revamp, another achievement tier was added for a second Baal. Not everyone will combine it to form Cronus though, as it's a nice wearable on its own. In fact, I didn't even create Cronus with my first one. I kept the Baal as a wearable. I only created Cronus in January when the second Baal achievement was added.

I'm sure you'll find a buyer in time. You may have to keep it in trades for a bit, but that's the way it goes with many expensive weapons. Good luck selling if that's the route you take. :)