One of the issues with Avgas and hence it's price is the lack of leaded car fuel. I attended a Shell seminar some while back and they were saying if Avgas previously never reached the "cut" during manufacture, they would reprocess it into motor vehicle fuel by blending it........ however since the loss of leaded car fuel in Europe, now if it fails to come up to spec they pay companies to dispose of it for them by burning the batch and filtering the emissions.....
I do not know if this still continues, but it wouldn't suprise me at all.