Last I heard the cost was around $600 seemed like it was justa way to weed out the weekenders.
I have a friend that retired last year with a gun store. He sold over 40,000 guns. Over 500 the week he closed. It was crowded.
The paper work was a nightmare for him. Although they were very meticulous it is hard to imagine how you can innocently get boxed in to trouble.
I was around when the ATF would pop in unannounced to check the books. No official attire, they would like a construction worker or hunter hanging around then show a badge and ask to see the books.
You are required to keep all paper work as long as you are in business, and duplicate copies here for the state even after you go out of business for something like 10 years.
The FBI or ATF could call anytime for a record search that you are required to do in a timely manner(right now) at your expense. I saw his wife doing lenghty searches through 40,000 documents time & time again. A couple times the ATF would call the next day saying Oh we made a mistake it was another dealer.
When he closed he had to get permission at several levels(nearly impossible) to transfer the document to ATF ownership. He had to hire a bonded carrier to transport them. During transport he was called for several searches and even threatened by the ATF for failure to comply even though he had permission.
The worst problems for him came doing FFL transfers(Nightmare) and people who LIE having legal issues. I have seen gun transfer be approved, then have the ATF call revoking it as he is handing over the gun. Or have the waiting period with the ATF approve and the local police department say NO Go.
The list goes on but you are not selling candy bars so you need to be able to read or judge people. It is so easy for you to end up on the wrong side.
Here is an actual example, A guy walks in well dressed asking to do an FFL transfer. He agrees to the fee and says he knows about the form requirements/waiting period. He sends the signed FFL to the seller. The gun comes in but the buyer fails approval. The seller refuses to take the gun back. So now my friend has this guys gun he paid for but can't let him have it. The guy is pissed. After 1 year my friend is required to pay the ATF to field destroy the weapon.