morlock13: There is no such thing as a class 3 license. Never has been, probably never will be.
a3kid: Federally, it's a one-time $200 tax per firearm - individual states may have other requirements. Best place for that info is to look at the NFA FAQ at subguns.com
Individuals owning Title 2 (NFA) weapons, pay a making or transfer tax at the time the firearm is registered to them and entered in the NFRTR. The making tax is a one-time $200, and the transfer tax is a one time $5 (for AOW) or $200 (all others) payment, payable when the weapon is registered to a new owner. The tax is not a license - it is a one-time tax. Individual states may require a permit and/or permit fee, and some states charge a yearly renewal fee on that permit.
Dealers (type 01 FFL) who pay a yearly special occupational tax (SOT) to deal in NFA firearms are "Class 3" dealers, because that is their SOT class.
Manufacturers (type 07 FFL) who pay a yearly SOT to deal in NFA firearms are "Class 2" manufacturers, because that is their SOT class.
There is also a Class 1 SOT for importers of NFA firearms.