One shelf to read from, one to build from.

A price is not settled by its digits. It takes on meaning inside a comparison.

The question above has no answer until you say what you are comparing it to. That is not a trick; it is how judging a number appears to work. Below is what four papers report about it, and where this site stops.

Put the same price in front of the same person twice, with nothing between the two readings except an invented thing to compare it to, and the answer can move. The price did not move. What moved was the frame it was read in.

Four ideas cover most of that. Anchoring: a number you saw first tends to become the starting point for the estimate that follows. Reference points: outcomes tend to be judged as changes from some baseline rather than as absolute amounts. Framing: the same content described two ways can be chosen at two different rates. Mental accounting: the satisfaction of a purchase seems to split into what the thing is worth and how the price compares to the price you expected.

For someone selling on X, the useful part is not "anchor high". It is that a buyer who cannot tell what your offer should be compared to is being asked to do the comparison work themselves, and may simply stop. Naming the comparison honestly — this is a month's coffee, this is not a replacement for your accountant — is a service, not a lever.

The same knowledge points the other way just as easily. Manufacture an anchor that was never a real price. Frame a loss to make a deadline feel like a threat. Suggest a purchase comes out of a wallet it does not come out of. This site does not do those things, and says so where it would be most tempted to.

These papers report tendencies, not laws, and none of them were about this product. Nothing here is evidence that US$39 is the right price for Chapter 1. What this site is willing to say about that number is on the Chapter 1 page, where it is written down as a launch price — set to find out whether the chapter lands — rather than as a figure anyone has justified.

Sources for "Is $39 expensive?"

• Tversky, A. & Kahneman, D. (1974) Judgment under Uncertainty: Heuristics and Biases
  Science (DOI) — Reports that a number seen first can become the starting point for a later estimate, and that people adjust away from it too little. This is where the word anchoring comes from.
• Kahneman, D. & Tversky, A. (1979) Prospect Theory: An Analysis of Decision under Risk
  Econometrica (JSTOR) — Argues that outcomes tend to be judged as changes from some reference point rather than as absolute amounts. The term reference point is borrowed from here.
• Tversky, A. & Kahneman, D. (1981) The Framing of Decisions and the Psychology of Choice
  Science (DOI) — Reports that the same content, described differently, can be chosen at different rates. This is where framing comes from.
• Thaler, R. (1985) Mental Accounting and Consumer Choice
  Marketing Science (INFORMS) — Splits the satisfaction of a purchase into the worth of the thing acquired and the gap between the price paid and the price expected. Mental accounting and transaction utility come from here.
• Thaler, R. (1999) Mental Accounting Matters
  Journal of Behavioral Decision Making (Wiley) — The author's own later review of that framework. Easier reading if you want to check how the terms are defined.

The problem is not the number. It is how much work choosing costs.

Twenty-four jams or six. The famous study is real, the replication record is messier than the story that travels, and both facts matter if you are deciding how many things to put on your own sales page.

The study people quote put jam samples on a supermarket table: twenty-four varieties on some days, six on others. More varieties drew more people to stop; a smaller share of those people bought. That is the whole finding, and it is worth reading rather than repeating.

What usually gets left off is what happened next. A meta-analysis pooling 50 experiments found a mean effect close to zero, with large variation between studies. A later review of 99 observations found the effect does appear, but under conditions: when the set is complex, when the task is hard, when the person is unsure what they want, and when they are trying to spend as little effort as possible.

So "fewer options sell more" is not a law you can apply. What survives is smaller and more useful: choosing costs the buyer work, and you can reduce that work without taking anything away. Give the set an axis — morning, afternoon, evening; first purchase, second purchase — and twelve options become navigable. Removing options is one way to make choosing cheap. It is rarely the only one, and it is the one that costs your buyer the most.

If you are selling on X, the practical version is a single question: what does a person have to decide before they can decide to buy from you? Every answer on that list is work you could have done for them.

The three papers below disagree with each other in places, which is why all three are linked rather than only the first. This site takes the direction of a tendency from them and nothing about effect size. None of it is evidence about any price on this site.

Sources for "Are more options always kinder?"

• Iyengar, S. S. & Lepper, M. R. (2000) When Choice Is Demotivating: Can One Desire Too Much of a Good Thing?
  Journal of Personality and Social Psychology (PubMed) — Three studies questioning the assumption that more options always motivate more. This is the starting point of the subject, not its conclusion.
• Scheibehenne, B., Greifeneder, R. & Todd, P. M. (2010) Can There Ever Be Too Many Options? A Meta-Analytic Review of Choice Overload
  Journal of Consumer Research (Oxford Academic / DOI) — Pooling 63 conditions across 50 experiments and 5,036 participants gives a mean effect near zero with wide variation between studies. Cited here to refuse the claim that more options are always worse.
• Chernev, A., Böckenholt, U. & Goodman, J. (2015) Choice Overload: A Conceptual Review and Meta-analysis
  Journal of Consumer Psychology (Wiley / DOI) — From 99 observations and 7,202 participants, sets out four conditions — choice-set complexity, decision task difficulty, preference uncertainty, and a goal of minimising effort — under which the effect is more likely to appear.

You are not short of evidence. You are sitting on evidence you have not put into a shape that counts.

No sales, no reviews, no audience to speak of. This is the ladder of honest proof you can build from a standing start: specification, demonstration, a piece given away, the boundary of what you refuse to do, and your own method run against your own business in public. With the signalling research it comes from, and the two regulators who have already written down what happens when a seller invents the proof instead.

About fifteen minutes to read, with a five-minute inventory at the end. Free, in full.