The First Law of Economics

Or maybe it's the Second.

It doesn't matter, the point is that demand creates its own supply:

From the BBC: Man Convicted of Converting Guns
Englishman converted 90 replica MAC-10s to fire live ammo. This apparently went on for several years. Curiously, he was convicted of seven counts of "Conspiracy to.." do this or that, and the two charges of possessing a prohibited weapon were dropped.

Update: he got a life sentence.