This caught my eye too and initially I was set to buy a couple of pails. But it is expensive for sure even on sale. After some research I decided to mix my own green sand using supplies from my local pottery making supplier instead.
My green sand is still from about 20 years ago. Bought as bags from I don't remember where. It's coarser than I'd like but doesn't require a muller to reconstitute the burned petrobond which is one reason I've stayed away from that.
Just toss in some water and mix a day or two before.
I built a sand fluffer to break up the hard chunks. My Sand Fluffer