As for fair on a 12-8 learn the catalog prices for options plus the base cost of that model for a good starting point.
Here are some good 12-8s for practice to get you started. Add up what you think these cost from the catalog, the guys here will help you with it so you aren't waiting for just one person to answer you.
Don't look for the ivory as a option, it's here to show how wide the price range can be.