I wouldn't buy used unless you know the person you're getting them from. There are several lightweight wheel sets out there in the $500-$1,000 price range. I have the Ultegra 6700 Tubeless wheels on my bike and they have been a great set of wheels that handle the stress of my 225lb weight, nice and smooth hubs, 1600 grams, and road tubeless certified to boot. They are spec'd the same as Dura Ace C24 tl's but with an aluminum hub instead of titanium (200g weight increase over DA's). The 6800 11spd wheels can be had for around $500 if you shop around.