The thread below on sprung/unsprung weight inspired me to calculate the
cost - and to speculate on the value - of my latest weigh saving investment.
I thought I would share my results with you.

After having to give up on the third mountain in the Ötztaler Radmarathon
two weeks ago, I realized I had to loose a lot of weigh before my next
attempt.So I bought new very slim spokes ( 2.0-1.5-2.0 mm) to replace the
plain gauge (2.0) that the bike shop had put in, because they considered me
a heavy rider . i.e. 86 kg = 187 lbs. But Jobst Brandt's great book on
wheels has told me, that heavy riders don't need heavy spokes - just very
tight spokes and strong rims. So that's what I got. The weight saved on the
two wheels is 368 g.- and the price for the spokes & nipples is exactly 50
US $. This gives a price per saved kg of 136 $.

Is it worth that money? The following considerations tell me it is:

I figure, that if I want to make it over all four Alp mountains next year, I
will have to loose 7 kg - going back to what I weighed, when I was 40, -
gee! thats 15 years ago. Loosing 7 kg is worth 7*136 = 951 $ - and though
that's a lot of money to me, it is also a lot of work to drop 7 kg of body
weight and stay there. I mean, I do a LOT of cycling already.

So would I be willing to pay almost a thousand dollars for a weight loss of
7 kg, that would last for - say 7 years? Yes, definately, I think it is more
than fair - it is cheap, considering the effort of carrying that load up
5.500 meters in the Alps. So saving weight by putting in butted spokes IS
good value for money.

But I still need to find the limit for how much I would be willing pay?
Chosing between two different Shimano derailleurs, 105 or Ultegra, the weigh
difference is a mere 13 g and the prise difference is 14.29 $ - making the
price of one saved kg: 1099 $. Or 7,700 $ for loosing 7 kg. At that prise,
I would rather do the hard work or suffer the privations needed to loose 7
kg of body weight and keeping it down. Unfortunately I bought the Ultegra
Group already. What a waste!

So I look for my limit somwhere between those two exambles. I guess I would
be willing to pay 50 $ pr month to be 7 kg. lighter without really trying
(besides what I do allready) So if the weight saving parts lasts for 7
years, I guess 600 $ pr. kg saved weight is still a fair deal.

Now I have the rule of thumb I need, when I consider buying lighter parts
for my road racer: 60 cents per gram saved weight is my limit. Although I
think, that's a lot of money to be willing to spend, and wouldn't telle my
wife about it, there probably aren't many lighter parts available at that
price for my 10 kg middle level road bike. Maybe a saddle, maybe shoes. But
that will be it.

Ivar of Denmark