Same with HPF and many of the others that sell a version of this same 321 ss manifold.
They are way overpriced when you look at what you can get on Ebay, but then again, some of the companies are selling a complete kit, with fabricated DP, WG pipes, and all the stuff you need to pretty much just bolt on the manifold and a turbo of your choice.
If you don't mind doing the fabrication work yourself, and can live w/o the crack free warrrenty, then Ebay is the low cost route for sure.
Not everyone is willing to take the responsibility of buying off Ebay however, and they pay for it with higher costs on similar (or in the case you pointed out, exactly the same.) parts.