In theory you can predict the total cost for things covered by insurance, but there are many layers of complex bureaucracy involved and the insurance company is actively trying to get you to fall through a crack and end up on the hook for a real bill. The insurance company also is practically the arbiter of whether or not you did it correctly.

The best example, is that you can go in for a surgery or something at a covered hospital for a covered procedure, but you can be surprised because some doctor assigned to you isn't in your network. Sometimes this happens after you're already under knocked out for the surgery, so you can't practically consult your complex policy at the time.