I have bought Zu Audio cables new, used/demo and off of eBay. If someone pays $5 bucks and I pay $100 doesn't matter to me as much as what the value of the cable is in "my system". You get them 75% off - good for you, I hope you enjoy them! I paid 75% for Julians and I was giggling at the steal for the improvements it brought to my ears at the time.
If the cables are bought at a price then you must have felt they were worth that price at that time. If they bring equal or better than expected improvements to your system then what's the harm? Yes, if you had waited a year then they would have been cheaper. With that logic you can wait 10 years and get a steal at a garage sale but you'll miss out on some great music over that time period. As for dropping a quality product from my system because my neighbour got them cheaper, well that make no sense at all, to me.
I look forward to trying out new Zu products, at the price I'm willing to pay.
