Appealed twice and both times they denied it stating I didn't require the surgery despite the fact they pre-approved it and paid for all the in-network costs. I ended up paying it because I had the money and I couldn't handle the stress of a legal battle (which given what I've read is an uphill battle).

Sorry to hear that.. you can usually appeal up the food chain sometimes.. e.g. to your states insurance department if the plan is regulated by your state. And at the Federal level you can also submit a ERISA appeal. None of it is fun and then there are deadlines... Also if you are on an employer provided insurance plan, you can talk to your HR who will have an insurance rep who can sometimes make these things go away e.g. get them paid. If you are at a large employer that self insures and uses a third party admin (like Cigna) then they can tell the admin to negotiate with the doctor/hospital and pay it.