Quoted from bluespin:

These recent sales have happened in the last six months or so, and I think this was the sequence:
A non-booting project with a better playfield than this one, and a horrible backglass sold for $4000 in less than an hour and multiple people waiting in line to buy it per the seller.
A fully working 9/10 original Quicksilver sold for $8000 through a Pinside post, but no ad
A non-booting project sold for $5000
Another project with poor playfield touchups, but with all the new parts (except a playfield) needed for a restore sold for $6500.
$6000 for a fully working copy that needs a new backglass and playfield doesn’t sound out of line to me. You can buy a Mirco playfield for $800 and a backglass from bgresto for $300
@gorillabiscuits You should follow the link from post 875 in the Quicksilver forum. Quicksilver has probably the best sounds of all the classic Sterns, especially the siren. Quicksilver is such a tough game that when you actually collect the siren it’s really satisfying. I’d rank the toughest early solid states as; Flash Gordon (toughest), Quicksilver (2nd) and Paragon (3rd).
https://pinside.com/pinball/forum/topic/quicksilver-club-all-welcome/page/18