Published: 03 June 2026 by Dan Williams
Series: Notes on eBay & Discovery
Observations on how collector behaviour differs from typical retail shopping, and why that may matter.
Most online shopping advice assumes buyers behave in a broadly similar way.
Someone identifies a need, searches for a product, compares a few options then makes a purchase.
For many verticals or categories, that is perfectly reasonable.
However, after several years of selling stamps on eBay, I am becoming more convinced that collectors tend to behave differently.
Not better or worse, just differently.
And if recommendation systems are built around buyer behaviour, those differences could matter more than many sellers realise.
The Typical Shopping Model
Imagine somebody needs a replacement phone charger.
The process looks fairly straightforward.
They search for a charger.
They compare a handful of listings.
They buy one.
The shopping mission is complete.
The buyer may never think about phone chargers again until the next one breaks.
Many online marketplaces were originally designed around this type of behaviour.
The challenge is helping the buyer find the product they need as efficiently as possible.
Collectors Often Have Different Goals
Collectors frequently arrive with a different mindset.
Sometimes they know exactly what they want.
A specific stamp or a particular variety, or a missing item needed to complete part of their collection.
But often the goal is broader.
They may be looking for:
- something unusual
- a better example
- a scarce variety
- an interesting postmark
In many cases they don’t know exactly what they will buy until they see it.
This process is often closer to exploration, or window shopping, than simply shopping.
Browsing Is Part Of The Hobby
One thing I have thought about repeatedly is that collectors often spend time browsing.
When browsing and buying: I view related items, I compare examples, I move between categories, I revisit sellers, I save searches, I save sellers.
And this behaviour, in myself and others, makes perfect sense.
For many collectors, the act of searching is part of the enjoyment.
Finding something unexpected can be just as satisfying as finding something specific.
That is very different from somebody trying to replace a broken appliance as quickly as possible.
Collectors Tend To Buy Thematically
Looking through my own sales history, I often see buyers purchasing related material together.
For example:
- multiple Machin varieties
- watermark varieties from the same reign
- regional issues
- stamps from a similar period
The purchases are rarely random and are often reflecting a collecting interest.
This creates patterns, and recommendation systems can potentially observe these patterns.
The marketplace does not need to understand philately, coin collecting, art or anything about collectables.
It only needs to recognise that buyers who purchase one item often show interest in another.
Repeat Buyers Matter
Another characteristic of collectors is the tendency to return.
A collector may not complete a collection in a single purchase.
They may revisit a seller weeks or months later.
Some buyers appear repeatedly in my order history, often purchasing material from similar collecting areas.
This behaviour is valuable because it creates a longer relationship between buyer and inventory.
The shopping mission is not necessarily finished after a single transaction.
Discovery Often Beats Search
This is one of the reasons I have become more interested in recommendations.
A search can only help a buyer find something they already know how to describe.
Discovery is different.
Discovery helps a buyer find something they were not specifically looking for.
A collector searching for a watermark variety may discover:
- a booklet pane
- a phosphor variety
- a related issue
- another item from the same collecting area
Sometimes the most satisfying purchases begin with a completely different search.
Why This Matters
Many of the publicly available articles on Recommender Systems from eBay discuss:
- recommendations
- co-purchases
- co-views
- related items
- buyer behaviour
Viewed through the lens of collecting or browsing, and this makes a lot of sense.
Collectors naturally create rich behavioural signals.
They:
- browse
- compare
- revisit
- purchase thematically
Those behaviours generate connections between items that recommendation systems can potentially learn from.
This does not mean marketplaces fully understand collectors.
It simply means collector, browser, or window shopper behaviour may provide useful information.
A Different Way Of Thinking
When I first started selling on eBay, I tended to think primarily about individual listings.
Today I’m think about collections of listings more often than not.
Not because I expect buyers to purchase everything.
But because collectors often move through inventory in ways that are difficult to predict from a single search query.
A buyer who arrives looking for one item may leave with something entirely different.
Or return weeks later for another item from the same area.
That behaviour feels entirely normal within collecting.
Closing Thoughts
The more I think about my eBay sessions and look at sales orders for buyer behaviour, the less I think collectors fit the traditional retail model.
Collectors browse.
Collectors revisit.
Collectors compare.
Collectors often purchase thematically rather than transactionally.
That does not make them unique.
But it does make them interesting.
And if modern marketplaces increasingly optimise for buyer journeys rather than simple search results, understanding how collectors behave may be just as important as understanding the products themselves.
— Dan Williams
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This note forms part of Notes on eBay & Discovery: a collection of observations about visibility, recommendations and buyer behaviour on modern marketplaces.