Why do identical peptides vary so much in price between vendors?

Two vials with the same label are often not the same product. Most of the price gap is in what you can't see on the sticker. Main drivers: - Testing. Per industry production references, purification is the biggest cost in peptide manufacturing, and a full QC panel for one batch can run into the thousands. Cheaper material often skips some of that testing. - Actual content. Independent labs catch underfilled and overfilled vials, so two "10mg" products can hold different real mg. Finnrick reports over 8,000 tests across 225 vendors and says purity and quantity vary widely between sellers. - Public COAs. Vendors who pay for batch-specific third-party results you can look up (such as Janoshik's verify.janoshik.com) carry that cost. "Email us for a COA" sellers usually don't. Scale and where it's made matter too. A low price can mean lower purity or less content, not a bargain. These are research-use-only materials. Compare a current third-party COA, not the sticker alone.