I, not being Jewish, probably am not one to speak on this. However, in the context (the Abraham story), I do not consider "jewing down" a slur. It seems, in this case, to be an attribute that even God honors. Nothing wrong with someone trying to get the best deal possible.
There is an art to haggling. I wish I were more adept at it.
(Incidentally, I do not use the phrase "jew down".)