I am often flabergasted by the low C150-152 Vref values quoted by AOPA and others. I recently spent some time talking to an insurance rep from AOPA about this, here's the scoop:

Vref is oriented towards the insurance industry, and they want to fudge on the low side. They typically state a value about $5-10K below true market value. This works ok for a $150K Bonanza, but not for a $30K Cessna.

This is why they say a decent 1967 150 with medium engine time is worth $15K when you can't find one for under $20K.

It get's worse the higher up the peformance and mod scale you go. For example, a 160HP Aerobat like mine tops out at $24K on their scale. The airplane is easily worth $40K.

I tried talking to the Aircraft Blue Book guys once at Oshkosh about this, they seemed to have little interest in any airplane that was worth less than $45K. Their attitude was that "real airplanes" sell for more than that, and anything below that is like buying a 1970's era Ford Pinto, i.e. "hey it's a car, and it drives fine, but even if it's in brand new condition, it's only worth $500 tops."

Clearly, these groups are out of touch with us guys at the grassroots level, and they simply aren't interested in being more accurate about it.