The only real upside of Dura-Ace cassettes is the weight reduction from the largest 3 or 4 titanium cogs that are connected together with an alu spider.
The rest of the steel cogs are essential the same as the ones found on cheaper, such as Tiagra cassettes. If you are like me, and wear out the smaller cogs first, I would just replace these, and mate them up with the Dura-Ace spider and big cogs. At my local bike Co-op, we have 100 pounds or so of such stuff, at a cost of $5 per cassette. I found a decent SRAM Red Powerdome and a nice Campagnolo Record 11-speed cassette in the bin yesterday.
BTW: be careful about buying used cassettes online. I've seen cheap cassettes mated with Dura-Ace and Ultegra lockrings, and fobbed off as being the real thing.