The MAGNEX one says its made from high quality stainless steel...
The piper one says its just "MILD steel" which is the same material as a normal standard back box (the kind that last 3-4 years)...
BUT
you normally get a lifetime guarentee with most stainlesses...
I imagine theyd sound completely different too (magnex much louder)...
SO no wonder theres a price gap..
if you want a stainless.. get the magnex!