price of WireWord ECLIPSE III DISCRETE BIWIRE

It's a private seller, and I would only buy if I can try them first. It is the copper version, not the silver or gold version, which were more expensive. Seller is reluctant to let me try first. So we'll see.

Why would you think a private seller would ship you a set of cables for a free trial.  If they are used and you want them then buy them.  If you don't like them re-sell them like he is doing.  These used equipment sites are not Amazon.  

That's a pretty big ask from a private seller.

I agree with @jackd , if you think you want them and the price is right, buy them and give them a shot.
You might love them.
But if you don't like them, put them back up for sale.

see if he will give you a trail period if you pay for them first.

wireworld today makes very well built (if rather high priced) cables

they have a terrific record for quality and good sound stemming back from their start some 20 years ago - to me, their higher value cables are excellent

as many successful cable makers do, they have some very very expensive products for that segment of the buyer market... which i generally avoid