How much should I pay for a 2001 Thiel CS 3.6?

If you're not worried about cosmetics, they're of a very good built quality. They're extreamly hard to drive but you don't have to break the bank. You can use pro grade amp or any modern class D(or T) amp that will be in low thousands range.

I'd say $3k may be too much and you should try to get as
low as possible. If you reach $1500, you'll hit the bull's eye. Be argumentative when you try to 'lowball' stating that it may be the time to change woofer that could go bad in few weeks and it's $$$amount of money per each side...

Depending on your project set up and room, these speakers might not do the best job for you so you gotta be more flexible with your choice.

THIEL speakers are very detailed but can sound a bit forward in the upper-mids and trebles. they are miles better than a boomy speaker from Best Buy however.
a couple of grand shouldn't even be too much to spend if they are really well cared for but look out for tipped-up high frequencies. i even got to hear the big beautiful CS-5's one time and they were very coherent and powerful, but there was that prominent high-frequency edge again in a speaker that should have been beyond reproach. really excellent build-quality though.

Hi guys
Thanks A LOT for the helpful info. My situation is that I was planning a modest setup -to spend up to $1500 on speakers and pair them with a NAD 356BEE amp (e.g. was considering B&W). All of a sudden came across this unique opportunity with the 10-year-old Thiels which are obviously orders of magnitude better on paper but (1) I'm concerned I may not have the expertise to verify they are in good shape (2) I'm concerned about having a very non-matched setup where they will not sound good with a $800 80w-per-channel amp.. Cant afford more now.. But may b golden opportunity.. Any thoughts are welcome I'm such a novice in audiophile world.. Cheers and thanks again

If you can't afford to power the Thiel 3.6's, you'll never get all they're capable of.