I need to remove my ex wife from my LLC and business account. How much does it normally cost on average?

If your wife is agreeable, it should not cost much. But I recommend you use a lawyer whether she is or not. There are a number of things that should be addressed in writing in case things become disagreeable later.

Changing the membership interests of an LLC is not difficult, however, it needs to be done correctly or it will likely result in litigation. You can file the changes with the AZ Corporate Commissioner. You need to file Articles of Amendment. That's the easy part. You also need to revise and update your Operating Agreement. That's the hard part that requires an attorney. If you do not have an Operating Agreement, you should.