There’s also the fact that it’s a pre-1986 machine gun. Machine guns manufactured after that period are illegal to own as an unlicensed civilian in the US. The fact that it’s a legal machine gun adds a few zeros to the overall value. Beaten up M16s receivers (the serialized bit of an AR-15) can go for over $10000 alone and you still need to build the rest of the gun on that receiver. All of that money just to have a legal machine gun in the US