About 20 years ago, here in York, PA, there was a gun buyback program. They were paying about $50 for a working gun. Some unknown wonderfully sick son of a (well) gun was passing out hand written leaflets showing how to build a single shot, but working firearm with materials cheaply available at any hardware store. He wrote that if you made and sold ten of them, you would have enough money to legally buy a good gun.
And there was the time when SKSs were cheap and people would buy them and take them to the “buyback” for a profit.