The markup in one sentence.
A Brother TN-2420 OEM toner sells at about £55 and lays down 3,000 pages. A reputable compatible for the same printer sells at about £14 and lays down the same 3,000 pages. That is roughly a 4× multiplier on an identical piece of physical work — a plastic hopper filled with thermoplastic powder. The printer manufacturer subsidises the printer and taxes the consumable. It has been the standard model since the 1980s and nobody enforces it more aggressively than the top three laser brands.
When OEM actually earns its price.
Colour laser on graphics-critical work. Photocopy-grade legal documentation where a page smear can matter. Any printer still in its first-year warranty where the manufacturer will use a compatible cartridge as a warranty-void excuse (HP, Brother and Xerox all historically have; Canon is less strict). And any device on a fleet managed print contract where the contract locks you to OEM — no choice, live with it.
Everywhere else, buy compatible. Mono office laser, receipt printer, anything under thirty pages a day, anything the printer would need replacing on before the manufacturer would honour a warranty claim anyway.
Reading a page-yield figure.
Page yield is a standardised number. ISO/IEC 19752 for mono, ISO/IEC 19798 for colour. Both assume 5% ink coverage per page — a typical text-heavy business document. Real yields drop the moment you print heavier: a page with a company logo, a scanned form or a photo embedded eats 10–20% coverage and you get roughly half the rated yield. So a 3,000-page cartridge realistically prints 1,500–2,000 real business pages if your documents include images. Divide the cost by the real yield to get true cost-per-page, not the marketing yield.
Compatible quality tiers.
- Tier one · Rebuilt OEM. Empty OEM shell, re-manufactured to spec, sold by companies with ISO 9001 quality systems. Same drum, same rollers, refilled toner. As close to OEM as a compatible gets. Buy this for anything printing more than fifty pages a day.
- Tier two · New-build compatible. Made from new parts by a third-party manufacturer. Quality varies. Buy from a brand with a warranty and a returns route, not a marketplace listing.
- Tier three · Refilled OEM. Someone drilled a hole in an OEM cartridge, poured in generic toner, sealed it. Cheap and unreliable. Skip unless you have zero printer downtime cost.
The chip lock.
Every OEM cartridge sold since about 2015 has a microchip that reports its status to the printer. HP have been the most aggressive about pushing firmware updates that reject compatibles — the "Dynamic Security" scandal — and were sued for it and lost. They still ship the mechanism. Modern reputable compatibles ship with replacement chips that pass authentication; check the compatible seller states this explicitly for post-2020 HP printers.
A working rule of thumb.
Under thirty pages a day, buy any decent compatible. Thirty to two hundred pages a day, buy a rebuilt OEM. Two hundred plus a day, buy OEM and negotiate the price with your supplier — at that volume you should be paying twenty to thirty percent under RRP or you are being overcharged. Above that, you are on a managed print contract, in which case none of the above matters — the contract is what you are buying.