Why Two Quotes for the Same Specification Differ Threefold
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Three suppliers quote against the same specification and the spread is wide enough that at least one of them must be lying. Usually none is. The quotes describe three different processes, three different cost bases and three different levels of documentation, and the specification they all reference is the part they agree on rather than the part that sets the price.
Understanding where the difference comes from is worth more than another round of negotiation, because it tells you which quote you can actually live with.
One: the route
For a substance available by more than one route, the routes do not cost the same and do not produce the same impurity profile. A chemical route built on a steroidal starting material and a biological route that generates the target structure have different raw material costs, different cycle times and different purification burdens.
This is the largest single source of legitimate price difference, and it is also the source most invisible in a quotation. Two suppliers can both meet the same specification while running processes whose cost structures barely overlap. The impurity consequences of the choice are set out in how UDCA is made.
Two: purification, which is where yield lives
Reaction yield is the number quoted in development reports. Isolated yield after purification is the number that sets the cost.
One additional recrystallisation can move a price by a double-digit percentage. It also moves the impurity profile, which is why two suppliers can be genuinely compliant and differently priced. A process that needs three purification steps to reach the same specification costs more to run than one that needs two, and nothing in the certificate reveals which one you are buying.
Three: scale, and the shape of the cost curve
Unit cost falls with campaign size, but not smoothly. Small campaigns carry setup, cleaning verification and analytical release costs spread over fewer kilograms. Large campaigns amortise those and then run into different constraints: solvent recovery capacity, drying time, warehouse space.
This is why a quote for one drum and a quote for twenty can differ by more than twenty times, and why a supplier quoting a small quantity at a large-quantity price is making an assumption about the future that you should hear stated.
Four: solvent recovery and waste
Solvent is a large line in most organic processes, and whether it is recovered changes the cost base substantially. A plant with recovery capacity buys less fresh solvent and pays less for disposal. A plant without it pays both.
The customer never sees this line. It appears as a price difference that looks arbitrary and is not. Our note on recovered solvents and mother liquors covers what recovery does and does not change about the material.
Five: how much testing and documentation is included
| Cost line | When it becomes the difference | Can a buyer verify it |
|---|---|---|
| Route | When more than one route reaches the specification | Partly, through impurity profile and process questions |
| Purification steps | Always, but invisibly | Indirectly, through batch data spread |
| Campaign size | Small quantities, and mixed campaigns | Yes, by asking about the campaign |
| Solvent recovery | Where recovery capacity exists or does not | Rarely, from documents alone |
| Testing scope | When full compendial testing is against a reduced panel | Yes, line by line on the certificate |
| Documentation and support | Regulatory packages, audits, technical responses | Yes, by counting what arrives |
The fifth line is where quotes become genuinely incomparable. A price that includes full testing against the monograph, a stability commitment and audit support is not the same product as a price for material tested against a reduced in-house panel, even when both say they meet the same specification. The gap between a supplier specification and an in-house one is analysed in supplier specification against in-house specification.
Six: what the supplier believes about the relationship
Not a cost line, and it moves prices anyway. A quote for a first order often carries an investment the supplier expects to recover later. A quote for a customer with an approved second source carries a different assumption.
This is the part of a price that is genuinely commercial, and it is also the part most easily tested: ask what changes at the second order. A supplier who cannot answer has not thought about the relationship. A supplier who drops the price sharply at the second order has told you the first price was not a cost.
How to use this in a comparison
Four steps turn a spread into a decision.
- Compare the certificates line by line, not the specification headers. Differences in testing scope explain a large part of a spread.
- Ask each supplier what campaign size the quote assumes, and what the price would be at half and double.
- Ask which purification steps the process needs, and treat an evasive answer as information.
- Ask what the price includes beyond the material: documents, stability, audit support, technical response.
A low quote is not automatically a risk and a high quote is not automatically safety. The question is whether the difference is explainable. An unexplained threefold spread means at least one supplier does not understand what it is quoting, and that is a risk regardless of which end of the range it sits at.
For the contract terms that should carry this understanding, see quality clauses in an API supply agreement. For what happens when the cheapest option becomes the only option, see dual sourcing and supply concentration.
Primary sources: the FDA Q7 guidance for the GMP obligations that sit behind the documentation cost, ICH Q11 for process description, and EudraLex Volume 4 for the inspection framework that determines what a plant must maintain.
Frequently asked questions
Is the cheapest quote always the riskiest?
Not always, and an unexplained spread is the real warning. A low price with a clear reason, such as a larger campaign or a simpler route, is normal. A low price with no explanation is a question, not a bargain.
Can two suppliers meet the same specification at different costs?
Yes, routinely. Different routes, purification depths, campaign sizes and testing scopes all produce compliant material at different costs, and the certificate does not reveal which combination you are buying.
Why does price per kilogram fall so sharply with quantity?
Setup, cleaning verification and analytical release are fixed per campaign. Spread over more kilograms they fall, and beyond a point other constraints such as drying and storage start to push back.
Should I ask for a cost breakdown?
You will rarely get one and it is not the useful question. Ask instead what campaign size the quote assumes, which purification steps the process needs, and what the price includes beyond the material.
Does a higher price guarantee better documentation?
No. It should be verified rather than assumed. Ask for the document set you need and check that it arrives complete, rather than paying for an expectation.
How do I compare quotes that use different testing panels?
Line by line against the monograph, with each difference identified and priced as a separate requirement. Two quotes are comparable only when they cover the same tests.