Why is printer ink so expensive?

Because the printer and the ink are sold as a linked system, priced so that the consumable carries the profit. The economics are deliberate rather than accidental.

The razor-and-blades model. Inkjet printers are frequently sold at or below manufacturing cost, sometimes far below. The manufacturer recovers the loss through cartridge sales over the printer's life — meaning the cheapest printer on the shelf is often the most expensive to own.

By volume, branded inkjet ink has repeatedly been calculated as one of the most expensive liquids consumers buy.

What else contributes:

Cartridges contain more than ink. On many designs the print head is integrated into the cartridge, so you replace precision nozzle hardware each time. This is a genuine cost, and it is why printers with permanent heads use cheaper cartridges.

Small volumes. Standard cartridges contain surprisingly little ink; "XL" versions are usually better value per millilitre.

R&D and chemistry, which are real but do not account for the margins.

Practices that attract criticism:

Firmware updates rejecting third-party cartridges, sometimes disabling cartridges that previously worked. This has drawn litigation and regulatory attention in several countries.

Chips reporting empty before the cartridge is, and refusing to print in black when a colour cartridge is low.

Subscription models that stop the printer working if the subscription lapses — even with ink installed.

Cleaning cycles consuming ink, particularly after periods of disuse, which is why an infrequently used inkjet can consume a cartridge without printing much.

What actually reduces cost:

Buy for total cost of ownership — check cost per page, published by manufacturers and reviewers.

Consider a mono laser if you print mostly text. Toner lasts far longer, does not dry out, and cost per page is dramatically lower.

Consider a refillable tank printer, which costs more up front and far less per page.

Print occasionally to prevent nozzle clogging.