Resale markets follow patterns that are consistent across very different categories of goods.
Depreciation curves
Steep initial loss then flattening.
Which applies to almost everything manufactured.
Information asymmetry
Sellers knowing more about condition than buyers.
Which depresses prices for everything in a category.
Trust mechanisms
Ratings, guarantees and escrow reducing that problem.
Platform fees
Commission affecting what sellers net.
Which shapes where things get listed.
Why condition information is worth so much
A buyer who cannot verify condition assumes the worst and prices accordingly, which drags down prices for genuinely good items.
Which is a well described economic problem and the reason every resale platform invests in trust mechanisms.
Photographs, service records, original packaging and honest fault descriptions all raise achievable prices because they reduce that uncertainty.
Timing
Seasonal demand affecting achievable prices.
Which applies to sports equipment, garden items and clothing particularly.
Refurbished markets
Professional refurbishment with warranty.
Which commands a premium over private sale.
Categories that hold value
Limited supply, durability and continued desirability.
Selling effectively
Good photographs, honest description and a realistic price.
Where the value actually goes
Between what a seller wants and what a buyer will pay sit platform fees, payment processing, postage and the discount buyers apply for uncertainty.
Which together explain why sellers frequently net far less than the listed price.
Understanding those costs before listing avoids the common experience of selling something and feeling it was not worth the effort.
Auction against fixed price
Different mechanisms suiting different items.
Which depends on how many potential buyers exist.
Local against postal sale
Collection removing postage and risk.
Which suits bulky items.
Buyer protection schemes
Platform guarantees affecting confidence and cost.
Circular economy effects
Resale extending product life and reducing consumption.
Why some things hold value and others collapse
Durability, continued demand, limited supply and the availability of parts and support.
Which is why a well-made tool from twenty years ago can outsell a five-year-old electronic device.
Anything dependent on a manufacturer's servers or software support loses value the moment that support becomes uncertain.
Fashion cycles
Items returning to demand decades later.
Which is unpredictable and real.
Counterfeits
Authentication as a service on higher-value platforms.
Which addresses a genuine problem.
Environmental case
Reuse avoiding the impact of manufacturing.
Which is substantial for most goods.
Buying used well
Ask specific questions, view where practical, and pay through protected methods.
Why it is worth knowing how these things work
Most of the systems that shape ordinary life are invisible by design. Nobody explains why a parcel took an odd route, why a film left a streaming service, why a wait extended, or why a price changed between two searches.
The absence of explanation is rarely deliberate concealment. It is that the people running these systems are solving their own problems, and the reasoning behind their decisions is obvious to them and completely opaque from outside.
Understanding the mechanism does not always change what you can do about it. It does remove a category of low-grade frustration that comes from assuming something is arbitrary, unfair or aimed at you personally when it is usually none of those things.
The pattern that recurs
Across almost all of these systems, the same three things turn out to be true. The behaviour that looks irrational from outside is optimising for something the observer cannot see. The cost that seems unexplained is usually concentrated in one specific stage of the process. And the information that would resolve the confusion is generally published somewhere and read by nobody.
That last point is the most useful. Regulators, operators and industry bodies publish an enormous amount of explanatory material that answers exactly the questions people complain about not being able to get answers to. It is dry, it is not promoted, and it is free.
A note on sources
Where regulation is involved, national regulators publish the actual rules and they are generally clearer than press coverage of them. Where an industry is involved, trade publications aimed at people working in it are considerably more informative than consumer coverage.
Practices described here vary substantially between countries, and anything with legal, financial or medical consequences warrants checking against the rules that apply where you are.
The pattern that recurs
Across almost all of these systems, the same three things turn out to be true. The behaviour that looks irrational from outside is optimising for something the observer cannot see. The cost that seems unexplained is usually concentrated in one specific stage of the process. And the information that would resolve the confusion is generally published somewhere and read by nobody.
That last point is the most useful. Regulators, operators and industry bodies publish an enormous amount of explanatory material that answers exactly the questions people complain about not being able to get answers to. It is dry, it is not promoted, and it is free.