Originally Posted by grolby

I didn't think it was cherry-picking, seeing as I addressed that very point (which is not exactly a revelation, returns are ALWAYS diminishing): gains, however marginal they may be, are still gains and still relevant. There is a point at which you have decided that the gains are worthwhile, after all you are not riding a Schwinn Varsity, are you? What makes you think that deciding it's worthwhile to ride a 20lb Sora bike over a 40lb Varsity is less arbitrary than preferring a top-end 14lb carbon fiber speed machine? Because it's not. The line is necessarily always arbitrary, because we all have different value systems and interests that lead us to decide what we can afford and what's worth our time and money.

The lighter, more expensive bike is going be faster in both cases, and in both cases the gains aren't particularly large. A Varsity is not actually all that much slower than a modern entry-level road bike, especially not if you aren't competing. But do you really think it's not worth buying the modern entry-level road bike?

Even within the world of expensive bikes, there are significant trade-offs to be made. I ride and race on a nearly 19lb steel bike. For the same money, I could have had a very nice high-mid range carbon fiber bike, probably a good 2-3 lbs lighter than the one I have. Instead, I put my money into a custom frame that fits me superbly and gives me supreme confidence in the handling of my bike in crits and on twisty descents. But I necessarily am slightly slower up hills as a result. Though I do think having the right fit makes me faster on the flats and in criteriums, so that's complicated matters, hasn't it?

So what's worth spending for and what's not? Low weight or the perfect fit? Carbon fiber or steel? No matter what I do, I'm not being transformed from a nobody into a race winner, but it's still worthwhile to have a better tool for the job at hand. It's no more foolish to go for a faster bike even if the faster bike isn't faster enough to stop you getting dropped on group rides. It's only foolish if you're not getting your personal money's worth out of that decision.