What Dave was talking about with being licensed is a person with a Class III dealer's license can still purchase newly made full-auto weapons provided certain terms are met based on what you have in inventory or potentially need to have on hand for sales to military or law enforcement buyers. (Like the current US Army is in the market for an individual to sell them Stens...

but that is how the law is written ). You are limited to one of each model/variation but some post-ban dealer samples are only a few hundred dollars for full-autos.
Without the license you are limited to purchasing full-auto weapons that were produced before the May 1986 change in the law. Plenty out there but the prices have gone up considerably in the past 20 years.