Jody. ZQ is right. You have options. Please get informed and do your research. Otherwise leaving him in such conditions would not be the in the best interest of the animal. He will be better off being put to sleep. This may sound harsh but it's reality. I'm sorry your cat is in such pain. I hope you can work this out with your vet.
Hi Jody, if you can't afford the bill, you DO have some options out there! First, you can ask your vet if he will take post dated checks, and second, you can apply for Care Credit, which is a special credit card used for pet care only. Please, check these options out! I can't even imagine the pain your poor kitty is in w/ a broken jaw. There IS pain medication available. Definitely ask your vet about this.
By the way, if your kitty can't eat at all and after checking the above options out-and you still can't afford the surgery, then the best and kindest thing to do would be to put him out of his misery. I hope that it doesn't come to this, and wish your kitty a full recovery.
Please keep us posted!