Price check on Humminbird 1198C SI

Got a buddy of mine that's upgrading some of his electronics and looking to sell his 1198C SI unit. I know it can be networked with my Helix 10, so I am thinking of buying it to add to my boat.

What would you guys say is a fair price to offer for this unit? Prices online are all over the place. Feature wise, it's very comparable to my Helix for not being the latest generation.

You can buy a Gen1 Helix 10 SI for 939.00 brand new with a 2 year warranty, the 1198 will cost over 400 flat rate to repaired by humminbird. When you consider those 2 things it would have to be pretty cheap for me to buy it.

600-800 seems to be best price range.