I am in the process of putting together a S1000+.  So far, I have selected the A3 FC and LB2.  When it comes to gimbals, it is not clear to me what comes with it and what else is required to integrate the camera to control it and use it for FPV.  I was looking at the Zenmuse Z15 BMPCC and, I see it at BHPhoto for $999 and on Ebay someone is selling it for $3500.  I expect they are different or the more expensive one includes additional tech required to integrate the camera with the platform.  Any help would be greatly appreciated.

Since the Inspire came out the demand for the larger zenmuse gimbals have dropped significantly and so has the price. I think $3500 was the original price. I'd suggest shopping around.