You're absolutely right on the underdosing part, which is what the "adulterated" part of the quote I gave likely referred to.
For example, you may have seen this study on MT2, which found that most of the ones they examined were only 50% pure:
http://sci-hub.la/http://onlinelibrary.wiley.com/doi/10.1002/dta.1655/pdf
The cost of raws combined with manufacturing difficulty differs significantly from peptide to peptide, even if it's not great compared to the final cost. To give you an idea, here are the top several proteins/peptides in terms of highest cost for us, on a milligram basis:
- IGF-1 LR3/DES (by far)
- HGH
- CJC 1295/DAC (almost as much as HGH)
- TB500
(We don't sell HGH btw, but had it tested along with the others.)