I think it can varies from bass 2 bass.
The older ones do hold their value, I have always got back what I paid and in one case a little extra, So possible investments or safe bets.
I have had 2 Pre EB's a 77 and 83. Both 2 band, both very slightly different in sound, the 77 had the epoxy preamp and sounded slightly less harsh in the highs to my ears than the 83.
I have also had a couple of EB's (2eq's) laye 80's and 90's models and they have all been very good as well. The build quality has always been spot on.
I'm just one of those people Stingrays just don't seem to work for no matter how hard I try.