I've had a few so kinda keep an eye on the secondhand prices - I would put the used prices a tiny bit higher that that esp for a early (pre'92) or later (after they got all the CNC stuff and went back to high quality) - £1200 or so for a SS1, £1400-1800 for Thumb or dolphins or whatever (again the older ones) depending on how many strings they have and age/ condition etc.
Secondhand, and the older ones you can get an amazing custom quality bass for silly low money. The early ones have thin thin necks too - I used to have a 1985 thumb and the neck was so thin. The downside is sometimes the sound sits in the mix in really odd places.