It depends on what server you're on. I think I usually see them around for 5g, I'm on Teva.
I'm not sure why they're so expensive LOL. I still get debuffed all the time~ ==
Well on Teva if you see an Elderine Necklace worth over 6 gold its not worth buying or dont even try to sell one for more than 6 gold either. I know there is a person on Teva who is trying to sell a Necklace for 6.6 gold and he still cant seem to sell it so a Heavenly necklace of Elderine on Teva would be worth around 4-5 gold.
Im still deciding if I should buy one for myself I currently have 18 gold approaching 19 after I unload all my mats from KKP to the vendors and NPC. I still can't decide weither to buy one or just save up for a Shining Ring of Uruga after I hit 1 gem because then Ill have some extra money to spare to maybe buy another Uruga ring and perhaps a decent stated Lv 80 fighter top which ill enhance to +9 myself.