it'd cost the manfacturer $200 to MAKE each one, and customers would only pay $5 to TRANFERS an AOW
No if the person has the correct manufacturing license and SOT they do not need to pay the $200 tax on each one, that is just for everyone else.
The $5 transfer is not the problem either. The FBI background check and relatively long delay is. Along with various states that have different laws and interpretations than federal law on what a firearm is and if it is legal.
When you look at where most judges are sold, and you then look at what it takes to buy a gun in many of those places, these are people that can walk into a gun store and walk out with a gun. Impulse buy on a whim, like with most other products.
When you tell the average customer they will need to wait months, go through a thorough background check, get a specific signature from a chief law enforcement officer or make a trust, etc
Their eyes will gloss or roll over, and they will ask to see another gun.
If you also told them they would permanently be registered with the Federal Government, and that they would need permission from the ATF for various NFA items before they even legally cross state lines into states that allowed them, you could make even more people give up sooner.
Now to people that are firearm enthusiasts, such steps may just be another formality they will readily jump through for their next big toy. But for many people NFA stops the purchase. On top of that fewer stores have NFA items on display to even peak the interest of the casual consumer.
While the much derided judge can go on to be one of the most popular firearms in the USA even though it has poor ballistics because it can be readily purchased like any other handgun, a similar NFA item would have limited sales by comparison.