I own 1984 CO 26 hull# 316 "Dharma Rose" (Varuna was hull #324 from I have read). Mine is one of the few CO26s with the Contessa logo that was after the transition to lead ballast and improved cockpit, anchor locker, etc.
From what I can tell, 1984 and after... (lead ballast) boats are selling for about $15K to $25K depending on condition and if they come with trailer. A newer Yanmar or better yet, Beta 14, gets you to the top of the sale list along with asking price. Trailers are amazing tools for these boats too. My trailer has saved me tons of money by avoiding winter yard storage and labor rates.
I am currently restoring Dharma, and subsequently taking a year off to do it as I have a young 7 month old son at home. I have already purchased the Beta engine, and Monitor wind vane system (target to re-splash is spring 2019 to get the boat ready to sail to Bermuda in the Fall of 2019).
If you are looking to sell, let me know. I may be interested depending on the condition of the boat.
Hope that info helps...