I get you, I understand that. But time is expensive resource. And if you do have good experience with these kinds of material, you know that you will never efficiently process it by hydrometallurgy. Never hydro on "inert" powders.
We don´t speak about hobby refining here, this is pure profit thing, if it is not there, I won´t do 800 000 pieces of some low grade material.
From regular plastic, you won´t have practically none ash. From opaque plastic (obviously with some kind of filler), you get a decent ammount. But filler is usually light and cheap material like silica, titania or limestone. Which is easily wash away from the metallic portion.
Chemicals are last resort in large scale. Because chemicals are expensive. But there is one more expensive thing - and that is your labor and time. With scale, it somewhat shrinks, yeah, but it is still there.
I won´t ever trim 800 000 cards by hand. Period. Maybe there is somebody who will be willing to do that, but I certainly won´t.