Originally Posted by
Broctoon
It's an example of diminishing returns. Going from the cheapest cog available up to, say, a $20 All City one, there will certainly be an improvement, but it might be only 10% better in terms of real, noticeable benefits. To then go from $20 up to a Phil Wood or an EAI Gold Medal (like 100 bucks probably?), there might be only an additional 2-3% gain. How much benefit the Dura Ace model can offer is subject to debate. Obviously, the DA is better than your stock one, almost without a doubt... but it's probably not a lot better. Perhaps only a tiny bit, or perhaps enough to be noticeable while you ride.
Do you like the Dura Ace? Will it make you happy to see it on your bike? Can you afford it? If so, use it. If you'll only ride that bike twice a year, your kids are going without shoes, or you have to skip lunches for a week to afford the cog, send that silly thing back for a refund.
It sounds like maybe you haven't had a chance to use a nice cog. Sure some cogs are quite expensive and maybe not as worth it to some but they certainly quiet things down and run a lot smoother using higher quality parts. Dura Ace is a fine cog, not super expensive but of good quality and is a perfect upgrade from a low end cog. Certainly if you are not able to live because you bought a Dura Ace cog then maybe you really need to work out your life and get some help. I could understand if you were saying that about a Super Gigas or Gold Medal cog which are rather expensive but DA track stuff isn't so bad price wise.