Methodology

Most comparison sites hide how they work. We publish it. Here's exactly how every number on pepmg is produced — and how to check us.

current index built 50m ago · 2026-07-02T14:57:55.612Z

▸ 0 · Why this site exists

You've used the other kind of price list. You know the moves:

A price with no date. Cheapest… as of when? If a list won't tell you when a price was checked, assume it wasn't. Every row here carries its capture time and a link to the exact page we pulled it from.
A "Top 10" that's really an ad rate card. When ranking is for sale, the list is the product and you're the traffic. Our order is $/mg arithmetic. There is no price for position — the masthead counts our paid placements live (currently zero), and any commission we'd earn is labeled on its own row.
A "cheapest" number propped up by a bulk vial or a blend. A 100mg wholesale vial or a two-peptide combo will always "win" a naive sort. We flag both and keep them out of the headline comparison, so cheapest means cheapest-for-the-same-thing.
A price that's wrong when you land. Nothing burns trust like clicking through to a different checkout number. We re-audit every vendor feed on a 6-hour cycle and a QC gate blocks the deploy if a shown listing goes stale.

None of that requires trusting us — every claim above is checkable on any row of the site. That's the whole idea.

▸ 1 · Collection — first-party, live-captured

Every price on this site is read directly from the vendor's own live store — the same public product feed their own storefront runs on — then cross-checked against a fresh fetch before publishing. No middlemen, no stale caches, no guesswork.

We read public data only. We never log in, never accept site terms, never bypass a technical block, never collect personal data. We honor robots.txt and rate-limit politely with an identifying user agent pointing here.
Every listing is timestamped with when and where we fetched it — shown inline on every row, with a link back to the source page we captured from.
Prices are the vendor's current list price (a discount code may lower checkout further).

Why no "breadth" from third-party feeds? We tested an aggregated third-party dataset for wider vendor coverage and spot-checked it — the listings were stale and in some cases dead (a product still shown that the vendor no longer sells). A price index you can't trust is worse than a smaller one you can. So we removed it: if it's on pepmg, we pulled it live ourselves.

▸ 2 · Normalization (the hard part)

Raw vendor data is messy. We turn it into one comparable number — cost per milligram — and flag what shouldn't be compared head-to-head:

Size parsing from titles/variants ("60mg", "2×5mg", mcg→mg).
Discount-adjusted price when a public code applies.
Blends excluded — multi-compound products (e.g. BPC-157/TB-500) don't get a single-compound $/mg. (134 flagged)
Form-filtered — oral/nasal/topical variants are separated from standard injectable vials.
Bulk flagged — wholesale vials (≥100mg) are marked so they don't masquerade as the retail "cheapest." (59 flagged)
Statistical outlier guard — anything outside 0.2×–5× the compound's median $/mg is flagged, so one mispriced vial can't define the cheapest or the spread. (206 flagged)

From 606 raw listings this build, 323 survive as clean, comparable, in-stock retail rows.

▸ 3 · Ranking (money can't move it)

Tables sort strictly ascending by $/mg. Bulk and outlier rows are de-emphasized and pushed below clean retail. No vendor can pay to move up. Where a link earns us a commission or carries a pepmg code, it's labeled on that row and ranked by the exact same math — the sort ignores who pays. See /disclosure.

▸ 4 · Continuous re-checking

A separate job re-fetches every first-party vendor on a schedule and compares the live price to what's published here. If a listing has gone dead or drifted, it's flagged for removal or refresh — so "captured 4h ago" stays true, not just true once. The whole index is also an open feed: /api/prices.json — every listing carries its vendor, source, fetch time, and the flags above.

▸ 5 · What the receipt proves — and what it doesn't

Being honest about our limits is the point. A pepmg row proves exactly one thing: this was the vendor's listed price for this product at the time and source shown. It does not prove:

Purity or identity. We don't test product. Where a vendor publishes a Certificate of Analysis we'll link to it — labeled "vendor-published," because we didn't run the lab.
Current price. Vendors reprice without notice — always confirm on their site before buying (the source link is right there).
Checkout total. Our $/mg is the listed vial price; shipping, minimums, and payment surcharges are the vendor's, not ours.
An endorsement. A cheaper $/mg is a cheaper number, not a recommendation. We sell nothing and ship nothing.

If a number looks wrong, the receipts are right there — click the source, check the math, and tell us at hello@pepmg.com. We'd rather be corrected than wrong.

All products listed are sold by third-party vendors for laboratory and research use only (RUO). pepmg sells nothing, ships nothing, and gives no medical, dosing, or human-use guidance. Listings are price-tracking data, not endorsements.