How do I model twelve months of retatrutide across supply routes?

I am comparing three suppliers on documentation rather than on price.

I have worked this out and I would like someone to find the error, because I suspect there is one.

My working so far, for the record, is below, and I am fairly sure the error is in the unit conversion rather than the algebra.

Is my approach right even if my number is wrong?

The short version: unit price, carriage, testing, dead-space loss and wastage. The first is the one everybody compares and rarely the one that decides it.

Dead-space loss is small with fixed-needle insulin syringes — a few microlitres per draw — and substantial with detachable-needle luer syringes at 35 to 100 microlitres. Across twenty draws that is up to two millilitres of solution.

Change one number and it reverses: if B assays at 82 per cent, that is 8.2 mg for £52, or £6.34/mg, and the cheaper vial is now the more expensive peptide.

Independent testing prices at the services this community uses are published and are stable enough to model.

Larger orders are cheaper per milligram and concentrate lot risk. Price both.

Answering this needs the order size, because carriage and testing amortise very differently across one vial and across ten.

Cost per milligram is the wrong metric entirely if you are optimising for confidence rather than price, and it is worth saying which one you are doing before you build the spreadsheet.

Independent testing costs roughly the price of one to two vials at the services this community uses. On a two-vial order that is a fifty to a hundred per cent surcharge; on a twenty-vial order it is five per cent.

Larger orders reduce cost per milligram and increase exposure to a single lot, which is a real trade rather than a free win.

Fixed-needle syringes save more peptide than most price differences do.

Put another way, this is a spreadsheet question and doing it properly changes conclusions more often than people expect.

The full calculation: (unit price + carriage share + testing share) ÷ (nominal mg × measured content fraction × (1 − dead-space and wastage fraction)). Every term after the first is routinely omitted.

Carriage on international consignments scales sub-linearly with weight, which is the quantitative basis for order consolidation.

The caveat is that optimising cost per milligram optimises for the wrong thing if documentation and consistency are what you actually need.

Decide whether you are optimising cost or confidence before you build the model.

The honest answer is that the cheapest headline price is frequently not the cheapest outcome.

Wastage from a reconstituted vial discarded at the end of its in-use period is a genuine cost, and it is a function of the diluent volume chosen at reconstitution rather than of anything the supplier did.

Published content assay results across the independent services show nominal and measured content differing by one to ten per cent, which is the term that makes label-price comparisons unreliable.

Nothing here is medical advice, and research-use compounds are not approved for human use.

Divide by measured content, not by label claim. That is the whole correction.