I prefer, "You sir, have negotiated with me as would a Gypsy. I am cross."
Seriously though, kids used it all the time when I was growing up — I didn't even know "gyp" was derogatory until I was perhaps in my 30's. If I had to guess, young me would have suspected it was spelled "jip" anyway.
We told Pollack jokes too and I didn't even know it meant someone from Poland.
I was not very cosmopolitan as a kid.