In your favour: there are currently two on Sailboatlistings.com.. both have been for sale for over a year, one of them nearly two. Asking low $30Ks.. both back east, I think, so you'd need to try to find a west coast listing for a better comparison.
A Yachtworld search.. wide range of askings.. only one in Cali.
1975 Downeaster (Sail) Boats For Sale
As an 'East Coast' boat they are likely on the rare side here on the left coast, that may hurt your potential, however by the looks of it a low $20K listing should draw some interest depending on condition.