I’m sure you did your homework and did everything by the book, but I’ve seen enough both online and in my experience with old houses (commonly modified without permit) to have an appreciation for licensing and permitting requirements.
A few years ago my friends’ landlord tried to rebuild the house’s deck until it got shut down by an inspector driving by. I thought it was outrageous until I walked over and saw what was being built, which was a laundry list of engineering and design failures. After that I was thankful that the inspector noticed and stepped in.
Licensing (and permitting) doesn’t exist for the ideal case where people practice perfectly without licensing. It exists for the average case, where people like to guess and improvise.
> End results, costs <30% of anything comparable offered commercially.
If you did the work yourself I’d expect similar savings. I think this is an example of DIY labor, not the cost of licensing.