Straight answer on Clutch slave cylinders

I have called every major pantera vendor as to why the pantera clutch slave cylinder for the pantera is 3-4 times that of an ATE or Alfa spider slave cyl. i see limited inforation that yes indeed they do crossreference and interchange but the vendors just seem to play "dumb" for lack of a better word. If another part works just as well for $0 to $50 I dont see why I should pay a premium for a pantera part from a pantera supplier if something else works. I do care about my transaxle but as this is the first replacement item i have needed to purchase, naturally I am going to question the price. The part did nto come from detomaso i dont see an isis on y slave so it stands to reason these parts are probalby being marked up quite a bit. I have recived mixed reviews on the longthrow and its necessity with a dash one trans. BTW here is my car, thanks
Ryan