Cost benefit
Much more interesting than I thought it would be! Having had a rough look at what we could, I suppose, call loose data, I have come to the following conclusions:
1. Modern high performance bikes can weigh as little as 18 lb but cost between £1000 -£1400.
2. Old fashioned high performance bikes weigh around 24 - 29 lb and can be found in hedges or bought for up to £250, depending on how much work you are prepared to do yourself.
3. This is unlikely to make any difference to anything unless you seriously want to race.
4. Choice of your bike weight is, therefore, based on size of wallet and desired self image (i.e., old fart travelling gently, happy family out for a ride, father knowing tinies are having to put in 10 times the power to weight effort he is (see earlier posts), anal retentives in lycra travelling at speed of light, etc etc. Local topgraphy and reason for travelling ( Commuting, fitness, fun, enjoyment gained by shouting at motorists, etc, also major choice factors.)
5. It is a well known fact that if the human body travels at over 30 mph in the open air you will die*.
So, all in all it proves that cycling is (or aught to be!) a broad church and that a weight between 18 - 33 lb is likely to enable you to have fun regardless of hilly bits, and that if you want a seriously light bike it will cost you. Upgrading (?) from 33lb to 18lb will cost you around £80 per lb lost.
For that money you can buy at least a months worth of best bitter.
*I made this bit up. Actually you will die anyway.