Here are a few stories related to scores and admissions.
Person 1: Perfect GRE scores (seriously 170/170), 4.0 GPA 1 year paid ($50,000) internship at Harvard. Gets in at all the elite schools...except for Harvard!
Person 2: Near perfect GRE scores (165/165), near perfect GPA, 3 years research experience, admitted to Stanford.
Person 3: Mid-150s GRE scores, 3.5ish GPA, 3 months research experience, admitted to Stanford.
Person 4: Great GRE scores, near perfect GPA, lots of experience, rejected at mid-ranked school.
I think that alone should tell you that luck plays a very HIGH part in admissions. That's why people with less than stellar scores apply to places like CU Boulder and why people with amazing scores are afraid to apply at mid-ranked schools. I'm halfway convinced that the reason I was admitted was because I chose the perfect advisor at the perfect time. You never know if an advisor has funding (or will get the funding they're hoping for), if their students will graduate on time, if they took on too many students last year, so on and so forth.
Point is, I would never advise an applicant that has an amazing application with only average GRE/GPA to not apply to places like Stanford and CU. Scores only mean so much and you'll never know when they'll mean more or less.