Urgent care would have had something closer to a $100 markup than $2,000, because you’re only paying for a few nurses and doctors to be on call, not for having used the resources that are meant for trauma and acute crises.
That hospitals are required make up fictitious itemized explanations for their very real costs is indeed broken, but it’s a very small part of the overall issue.
If you called the hospital billing department and offered 20% of the overall bill, they would likely have immediately accepted; uninsured hospital billing has expected value on the order of 10% of outstanding balances, so if you give them more than they can get from sending you to collections, they’re usually happy to compromise much more steeply than the 60% “discount” they offered you.