One thing I think might be important to distinguish is how different companies coming out of YC (and not in YC) are in different stages. No matter how many times the partners told our batch to not compete over valuations, it still happened. Personally I felt like without a competitive price tag, we wouldn't be looked at as a promising company even though we had less traction than other companies. We had a (rightfully) pretty lame raise after YC. I think one thing that might help is to be explicit with the companies, give them some idea of what their perceived stage is and what valuation range would be a good place for them to start.