It is my opinion that DY jewelry offered for sale at IBuyLuxury on Ebay is no more "authentic" than offering to sell the Brooklyn Bridge at a discount!
I own multiple David Yurman silver/gold pieces purchased from Neiman and Saks, but I too was lured by IBuyLuxury's guarantee and prices so I purchased a bracelet they claimed was authentic David Yurman. I had my doubts as soon as I opened it up. The clasp did not hold when worn. I took it to my local Neiman and Saks jewerly counters and compared it to identical bracelets in the case.....proved my suspicions.....big Fake! I had a few emails with IBL and they did agree to take it back, less a percentage. Lesson learned on my end. Common sense should have been apparent that no one seller should have access to that much merchandise and claim it is "authentic David Yurman" or any other designer, for that matter. David Yurman Inc ONLY sell their pieces through reputable dealers. Honestly, if it sounds too good to be true, it usually isn't true. I am sure there are a few honest sellers on Ebay that do have authentic pieces for sale. You have to do your best to determine if you are being duped, or not, by asking as many questions as you need. After all is said and done, you have to be comfortable with your decision. That is the risk you take when buying anything on the internet. Just because they have some really "slick" internet storefront does does not make them reputable. Anyone can set up a website to look authentic, so if you have some doubts, go with your instincts.