The 1400/1500 autoloaders never had the following like the offerings by Browning and Remington . Complaints of fit and finish and not to mention durability marred the gun's reputation . There are a few fans out there (such as myself) , you would just have to wait and be patient if you wanted to sell . From what I've seen at the auction sites , $250 to $350 seems to be the norm .
I agree with Shley65. They just don't have the following that the Remington 1100 or Browning A-5 has. Maybe it's due to the alloy receiver.
My Dad has a 12 and a 16 that he bought in the late 60s/early 70s and never had a problem with them though.
His evaluation is about right with my inclination being to the low end.