How the ranking works
Every consumable listing gets one figure: price ÷ total weight, in pounds per kilogram. Resin uses pounds per litre, treating 1 kg as 1 litre, which is how the trade quotes it.
Bundles count at their total weight
A listing advertised as "4 × 1 kg" is counted as 4 kg. This matters more than it sounds: multi-spool bundles otherwise look expensive next to singles, and they are frequently the best value on the page.
Discounts are measured against the typical price, not RRP or an average
A discount percentage compares today's price with what the product has typically cost over the last 90 days: a time-weighted median of its real Amazon price history, where each price counts for as long as it lasted. A brief price spike cannot make an ordinary price look like a bargain, which is exactly what an average lets it do. Where we do not hold enough history, we show no percentage.
Product pages go further. They compare today's price with the typical price over 12 months, and show how much of that year the product was cheaper than it is now. We only show a 12-month figure when we hold close to a full year of history.
Amazon Warehouse is compared like with like
Warehouse stock — Amazon's own returned and open-box items — is only ever compared with Warehouse or used price history, never with the price of a new item. Where no such history exists, it shows as a Warehouse deal with no percentage.
Printers, parts and scanners are ordered by sales rank
They have no per-unit measure worth ranking on, so their lists start with Amazon’s sales rank, best seller first. The best-seller pages go further: each product’s position is a duration-weighted median of its sales rank through the year, so one busy week cannot put it at the top.
Printer reviews and the printer finder
Our printer reviews are desk research. The ease-of-use score comes from a fixed checklist of features, and the reliability indicator from Amazon buyer ratings, how long the model has been on sale and documented problems; the full method is on the reviews page. The printer finder applies a fixed points table to your answers, those scores and today’s prices. Commission plays no part in any of it.
When we show nothing
If a title does not state a weight we can trust, the per-kilo column stays blank and the listing sorts below everything that does. We would rather show a gap than a number we cannot stand behind.