The way it was explained to me isv that there are so many plastic feedstocks produced by fuel production that it's often most efficient to pay someone just to take it away.

That's basically the economic equivalent of having to pay to get rid of a fallen tree despite that tree then going on to be chipped and sold in bulk to whatever the nearest local place buying chips is.

The feed stock is basically worth nothing, it's the labor and energy investment that you add to it at every step that adds the value.