The short story is: Since 1934, the US Government has required a $200 transfer tax to be paid on any machine gun, short barrel rifle, short barrel shotgun, destructive device, and silencer. The tax was instituted by Congress essentially as a de facto ban on NFA Firearms. It was their hope that such a prohibitively expensive tax on such weapons would make them unobtainable for the average person. They also did not want to outright ban such weapons and cause bloodshed in an attempt to confiscate such weapons from their owners (hence the requirement for registration). As the tax has never been adjusted to keep pace with inflation, it is now more of a “nuisance tax” than a real barrier to owning NFA weapons.
Yes, unfortunately you have to pay it… no two ways about it. Everyone you’ve ever met that has a silencer has paid it. As we say, “You’ve gotta pay to play!” And just remember, $200 was a whole lot more back in 1934.