Typically after the fact permits cost double the normal permit fee but that is generally after you are caught or, more likely, ratted out by a neighbor. OTOH since there is generally not going to be a "rough" inspection on anything that is not enclosed, just getting the permit then calling for the final inspection should be regular cost. You might even get away with saying you didn't know about the rough when you called in the final but they may want you to open something up. Hopefully you didn't piss off the inspector and he will just believe you. Pictures of the stuff behind the wall will help if you are going the "no permit" route. Just take lots of them from different angles and get everything they may want to see. You certainly want lots of pictures of footings, foundations etc with a yard stick in the shot. You also want pictures of wires and pipes in walls showing the labeling on the wire/pipe, the penetrations of framing members and strapping/securing. Next time you want to do something those picture will come in handy for you too. It is easy to forget what is behind that wall.