But yeah, a lot of people buy expensive rides for the looks and have no idea what do do with them...
Just had my bike stolen last week in NYC
It's true that it is usually much cheaper to lose weight on the rider than on the bike, but for some people it is probably easier (and more fun!) to spend the money.
[1] 1.5 kg makes ~8.5 second difference over 2000m on a 3% slope hill http://www.analyticcycling.com/ForcesLessWeight_Page.html
[2] http://www.training4cyclists.com/how-much-time-does-extra-we...
A more realistic 400w + 120lb rider +3% grade for 2000km then a negative 3% grade for 2000km and a weight diffidence of .3lb for 300$. End result after 4,000km is less than 5 minutes wow that's worth 300$.
[2] 1 trip using human riders hardly qualify's as measurement. But even still measurement is next to meaningless you can detect cocaine on most people in an international airport that does not mean they have had anything but the most indirect contact with the stuff.
PS: Sure if your racing professionally then things change around, but that's a tiny portion of the bike community.
You are right - 200w is low - I just used the default values. If you look on Strava, most middle-of-the-pack people post power in the low 300watts.
1.5 kg is easily the difference between a < $1000 bike and a $2000 bike. Cycling (as a sport) has a lot of financially wealthy (but time poor) people (the same people who used to play golf). These people aren't interested in the cost effectiveness of an upgrade, just weather it will help them beat their friends up a hill on the Saturday ride.
Personally, I think using ~$200 carbon fiber water bottle cages to save 30 grams is a waste of money. But the truth is that the grams they save do add up, and the weight does make a difference on hills. If you don't care about money (!) then why not spend the money....
Alas, my bike was targeted and stolen. :(
As much as everyone obsesses over weight, it's not the only difference between a $500 bike an a $5000. The more expensive components are also going to have more-difficult-to-quantify benefits like fit and finish (i.e., look prettier). The higher-end components also work better: shifting will be much more consistent, bearings will roll more freely, brakes won't require as much force, etc.
This is analogous to a car magazine complaining about how a particular model has a "mushy gearbox." You can still drive it, but the experience isn't as nice.
In the range of most cyclists: having carried my $400 iron-frame bike up stairs and a friend's $1500 bike up same, the difference is certainly not "1/10 of 2lb".