Why peptide price comparison sites mislead: per-vial prices ignore net peptide after counterion, 95–99% purity, and $12–$45 shipping. Compare $/mg instead.
A peptide price comparison website aggregates list prices for research-use reference materials across suppliers and displays them side by side, usually sorted by price per vial. That sort order is the problem. A vial labeled "BPC-157 5mg" from one supplier and another labeled the same are not the same purchase: net peptide content after counterion and residual water can differ by 15–25%, purity specifications range from 95% to 99% by HPLC area percent, and landed cost adds $12–$45 in shipping before anything ships cold. The correct comparison unit is dollars per milligram of verified net peptide, documented on a lot-specific certificate of analysis. Almost no aggregator computes it. This page shows how to compute it yourself in about 20 minutes per candidate supplier.
Nearly every peptide price aggregator online is built on the same three data points: product name, vial size in milligrams, and advertised price. Some scrape supplier storefronts on a 24–72 hour cycle. Others are updated manually and go stale within weeks — check any of them against a supplier's live cart and expect 10–30% of listings to be wrong or discontinued.
What none of them capture:
Take any two candidate listings and normalize:
Effective cost per mg = (list price + allocated shipping − discount) ÷ (labeled mg × net peptide content × purity)
Worked example. Supplier A lists a 10 mg vial at $42 with $15 flat shipping across a 5-vial order ($3 allocated). Their COA reports 99.1% purity by HPLC at 214 nm and 82% net peptide content by nitrogen determination. Effective content: 10 × 0.82 × 0.991 = 8.13 mg. Cost: $45 ÷ 8.13 = $5.53/mg.
Supplier B lists the same nominal item at $34 with $18 shipping ($3.60 allocated), 96% purity, and no net peptide content reported at all. Assume the industry-typical 80% when it is undisclosed: 10 × 0.80 × 0.96 = 7.68 mg. Cost: $37.60 ÷ 7.68 = $4.90/mg — but with an undocumented denominator, so the true figure could land anywhere between $4.40 and $6.30.
The nominal 19% price gap ($42 versus $34) shrinks to 11% once normalized, and inverts entirely if Supplier B's actual content is 70%. This is the arithmetic that separates a real comparison from a sorted table. Our own documentation practice on this point is described on the quality page.
A price comparison that omits net peptide content is comparing the mass of the counterion as though it were the mass of the product.
Build a spreadsheet. One row per supplier, one column per field. This takes about 20 minutes for the first supplier and 8 for each after.
Suppliers who publish all fourteen are uncommon. Suppliers who publish four or fewer are the reason this exercise exists. Comparative notes on how several vendors present these fields are collected in our high purity peptides review and quality research chemicals suppliers write-ups.
Coupon inflation is the most common tactic. A product carries a $95 "MSRP" it has never sold at, then a permanent 55% site-wide code brings it to $42.75 — the real price, dressed as a deal. Comparison sites that scrape the pre-code price rank that supplier last; sites that apply the code rank it first. Both are reporting the same number.
Affiliate economics compound this. Commission rates in this category run 10–40% of order value, and comparison sites monetized on commission have a direct financial interest in ranking the highest-paying supplier first. Read the disclosure. If a site ranks 30 suppliers and links to 6, the other 24 are furniture. Our own program terms are public on the affiliates page precisely so the incentive is visible rather than inferred.
Volume pricing is the honest discount, and it is worth modeling: a 25-unit tier at 30% off a $42 unit price saves $315, but if the working burn rate is 3 vials per quarter, the last vials sit for 24 months and approach the retest date before use. Buying to a discount tier that exceeds the shelf life converts a 30% saving into a 100% loss on the tail units. Tiered structures are detailed under wholesale.
This is the part the aggregators leave out, and it is the part that determines whether the effort pays.
Skip it entirely if the total order is under roughly $150. Twenty minutes per supplier across four suppliers is 80 minutes. Saving 12% on a $120 order recovers $14.40 — about $11/hour of effort. Order from a supplier already qualified and move on.
Skip it if the work requires GMP, USP, or clinical-grade material. Research-use-only reference materials are not a substitute, cannot be made into one by comparison shopping, and no price on any aggregator applies to regulated supply. That distinction is spelled out under research use only. Sourcing for a regulated application from an RUO price table is a category error that a cheaper per-milligram figure does nothing to fix.
Skip it if the analytical method is insensitive to the variable being optimized. A method with 8% inter-assay CV will not resolve the difference between 97.5% and 98.5% material. Paying a 22% premium for the higher spec buys nothing measurable in that context, and the money is better spent on replicate injections.
Failure modes to expect even when the comparison is done well:
Comparison is step one of four. The suppliers worth a purchase order survive all four.
1. Screen on documentation, not price. Reject any supplier that will not send a lot-specific COA before payment. This eliminates 50–70% of candidates in most searches and costs nothing.
2. Buy one vial from each of the top 2–3. At $35–$60 per unit, a three-supplier trial costs $105–$180 — less than one re-run of a failed 96-well experiment.
3. Verify the received lot against the paper. Lot string match, seal integrity, cake appearance, and arrival temperature. Log it.
4. Re-qualify every 6–12 months. Suppliers change contract manufacturers without announcement. A qualification from 2024 does not describe the 2026 material.
The output of that process is a two- or three-supplier approved list with known per-milligram economics — worth far more than any aggregate table, because it is built on lots actually received rather than prices actually advertised. Questions about specific lot documentation can go through contact; scope and use limitations are stated in full on the disclaimer.
Supplied strictly for in-vitro laboratory research by qualified researchers and institutions. Not a drug, food, cosmetic or dietary supplement. Not for human or veterinary consumption. Not evaluated by the FDA.
Purity, identity and lot number, documented for the exact vial you receive.