Commonly known in this country as Cerrobend, but not a filler, but an aid to bending, and I think it contains a large amount of antimony.
I used it when working at R-R to help bend up custom SS window frames.
It is now known under another name that you can buy it under, but unfortunately I can't recall what it is.
I can say though, it is nowhere near the price you have quoted.
Bogs