Okay, let's do some quick math:
$3,000 for 17 trees = $176 / tree 1,700 bf for 17 trees = 100 bf / tree They are offering $1.76 / bf
Either the board feet estimate is significantly off, or they're wanting to harvest extremely small trees, or the trees are very short and squatty.
I would strongly encourage you to get in contact with a professional consulting forester for on-site technical assistance regarding these 16 walnut trees.
List of Professional Consulting Foresters: https://www.dnr.illinois.gov/conservation/Forestry/Documents/2016consultingforesters.pdf
Best of luck!