Price confusion vs blue book value?

[Number21]

I'm looking for an 01 or 02 2500 with a Duramax. The bank says they will only loan me 80% of the blue book value for trucks over 100,000 miles, which is what I want.

I'm trying to keep it under $15,000 for a 2500HD with about 150,000 miles and a Duramax. According to Kelly Blue Book, those are worth about $8-12,000 on the high end. According to craigslist, they are worth $15,000!

I just looked up a short bed extended cab that I like with 140,000 miles. They are asking $13999, KBB says $11,000 in excellent condition.

What is with the big discrepancy in the price? Do the diesels add that much of a premium? Are they extra high in my area for some reason? They seem to be pretty common. I don't understand, I'd be happy to pay the KBB high price all day long!