This is a continuation of Estimating Assembly Cost which has addressed some approximations in estimating between North American and Asian assembly houses as price per pin.
The question does not address number of items in BOM and how significant / insignificant a reduction in a BOM might be.
For instance, if I have a BJT that costs $0.03 and a diode that costs $0.03, I could (if allowed) replace the diode with the BJT and my parts cost would more or less be the same. But now I'll have one less item on my BOM.
For each item on a BOM, what rules of thumbs can be applied to estimate cost ?
For each item removed from a BOM, what rules of thumb can be applied to estimate cost ?