Most inventory apps assume you bought one thing at one price. Peptide buying is not that: one order covers a dozen compounds, shipping is a single line on the whole invoice, and the same compound comes back from four suppliers at four prices.
The number that decides your margin is not what the vendor charged for the vial. It is that, plus the vial's share of everything else on the order:
landed cost per vial = vial price + (shipping + fees + customs) ÷ vials in the batch
Buy 60 vials with $145 shipping and $60 of fees and every vial carries $3.42 before you have sold anything. On a $23 vial that is 15% of your cost, and it is the difference between a healthy margin and a break-even one. Track it per batch, not per year, or you will never know which order was the good one.
Restock the same compound at a better price and a single "cost" field overwrites the old one — so every unit you still hold from the first order is suddenly valued at the new price, and last month's profit changes. Keeping each purchase's own cost is what stops your history moving underneath you.
In the app
Every figure on this page is something PepStock keeps without being asked — landed cost per batch, each purchase's own cost, what every reseller is holding, and the per-mg ranking at one kit and at ten.
