I forgot to mention that it comes with both the transducers
Now you're talking a bit more to the right person, etc.
I'd go search eBay, "completed auctions," and see what similar offerings SOLD for on there. Then I'd research breaking it up into pieces as you'll probably net a few more dollars going that route.
The problem with selling on eBay nowadays are the fees. However, you should be able to lock down a value pretty easily using them as a guide.