Right now it is about 5 seconds / piece if you are fast and I probably have a couple of hundred to upgrade to 4, and this is pretty much why I have couple of hundred at 0 because it is so time consuming.
I would love to see "batch refinement" similar to batch selling and then you can refine the selected pieces in one go, for me I would have saved 1-2 hours only today by this feature. I guess you would start by picking the refinement level and then you would see the cost increase when you start the selection.
While we are at it it would be good to throw in option to turn of the animations as well, helpful when you are not using the "batch refinement".