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I was trying to get a feel for the probable higher volume cost of various
components based on known lower price breaks.
While there can be many factors involved which make this an impossible task,
a friend pointed out an approximate relationship which seems to work quite
well enough top be useful as a ROUGH rule of thumb.

"Prices decrease by the exponent of the volume"

Unit price = $X
10 price = X / log10(10) = x/1 = X (duh)
100 price = X / log10(100) = $X/2
1000 price = X /log10(1000) = $X/3
...
1,000,000 price = X/log10(1000000) = $X/6

Note that log(1) = 0 which mucks things up if you try to work backwards :-)

______________

You can also convert between medium and higher level price breaks.

eg if 100 price is $1 then 1000 and 10000 price may be expected to be

100          1
1,000       1 x log(100)/log(1000) = 1 x 2/3       = $0.66
10,000     1 x log(100)/log(10000) = 1 x 2/4     = $0.50

This curve is a surprisingly good fit to reality (at least for Digikey).

I tried it on various Digikey prices and plotted a graph for the LM324 -
chosen due to its low price and popularity allowing quotes for a wide range
of volumes to be available under the same heading.

A graph of LM324's per $ against log10(volume) is attached.
This would be a straight line if the assertion were true.
A least squares straight line fit is shown for comparison.
The match is close enough to be useful.
Real prices get cheaper faster than expected as volume rises and then fall
off to below expectations at highest volumes.

Attached graph is ugly but small :-)

YMWV !

        Russell "All models are wrong. Some models are useful" McMahon


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