Alex, in my opinion some of the guys are being a bit harsh on you. It sounds like you got shafted on this job and unfortunately that happens. If you have a truck and a saw, there will always be people to take advantage of if that is your game. It happened to me after an ice storm 10 years ago or so. Live and learn.
Anyway, the bottom line on this wood is that you want/need the firewood gone. It sounds like you made the $600 Craigslist offer on the assumption that $600 is a fair or even bargain price, based on your assessment of the retail value of firewood. The wood really isn't worth very much, it is the labor that gets it into burning condition (cutting, splitting, stacking, and then waiting) that adds the value. Offer it free on Craigslist. It really isn't free- the guy picking it up is doing the work that the person you paid should have done and is getting paid in firewood.
It will be a fair deal for the guy getting the wood and it will be gone. Gone is the outcome you are trying to achieve. You got screwed and the best you can do now it is give the wood away. You'll end up with the outcome you wanted (tree gone) and while you will know that one guy gave you a raw deal, you will sleep well at night knowing you gave somebody a fair deal. That is worth more than the few $$ you might eventually get selling the wood to somebody. In all likelihood, it will rot in the driveway before someone will pay you to take it off your hands, especially after the winter weather we've had with trees down everywhere.