Does anyone here know what value a Porsche 906 has? Or where I would go to find out?

There is one for sale but the seller is also unsure of the pricing.

 

The prices of a 906 carrera 6 very greatly depending on pedigre. They have been selling in the $300-400,000 range depending on condition and originality.

You may want to look at the web sites for the 904 store or carclassic.
Car classic has an unrestores original on their site for 550,000 euros ($600,000)

Good luck

 

Is the owner of that 906 not in touch with the 906 community? Sounds strange to me. You don't own a car like that and not know about it. Beware.
Tim