Example of the difference...
A part that weighs 2 pounds:
Total dollars equation estimates $72.645
$/lb equation estimates $36.33/lb (36.33*2 = $72.66)
This is how it looks for all the different parts.
Why would I see a fairly significant difference in r-square (98.5% vs 85%) when I change my dependent variable from Total $'s to $'s per lb? My independent variable in both cases is weight. Each equation yields essentially the same answer in all tests of weight (within .08%).
How do I know...