Why such a wide price range for private party sale?

I'm looking to buy a used Ford Ranger, I priced it as close to accurate as I could on KBB, NADA, and Edmunds TMV.

KBB says about $7,000 for fair condition, and a little over 8 grand for really good condition.

TMV seems to be the lowballer at around $3,500 in average condition.

And NADA says between $5,600 and $7,100 trade in range, I didn't see a private party value option.

Why is there such a crazy price range between the 3? I know KBB tends to be a tad high these days, but should I just average the three so I know what to offer the guy?

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