Sigma or OEM Sigma as Quantaray

I own a Canon Rebel XT and I've been looking at the Sigma 17-70mm DX Macro
as an general lens. I've noticed Quantaray carries the same lens that is
obviously made by Sigma for Quantaray. The Quantaray lens is $200 cheaper
than the lens carrying the Sigma brand name. If Sigma is the OEM for this
particular Quantaray lens is there a difference between the two? Is this
difference, if any, worth $200? All listed specs are exactly the same (as
expected) and they are identical except for the where the "Sigma" should be,
it's blank.

Thanks in advance.
Mike in Vermont

 

I'll tell you why the Quantaray is cheaper. Ritz Camera contracts with igma
for these lenses the same way WalMart squeezes their vendors. Make it
cheaper.
Bob

 

I noticed that the Sony 18-200 lens has identical weight, minimum focus,
Aperture range & number of blades, elements and groups etc as the Sigma
18-200. Makes me wonder if the Sony lens is made by sigma, or if they
are both made to the same formula, or if it is just a big coincidence...