I agree with Ewfflyer,
I never had less than 90% but still I can't say that my oral exams were easier because of that. I have many friends that scored 70%-72%and their checkrides looked exactly the same as mine....I wouldn't waste that $90 just to look better in front of the DPE...he will just see if you passed the test...
Some people say "everything over 70% is a waste"