When you buy a printer, it may seem that you have paid for the product and the transaction is over. But a few months later, you will need ink. When you buy a gaming console, you will need games and perhaps subscriptions. Even the phone you carry may lead you to cloud storage, paid apps, and other headphones and devices that work with it more seamlessly.

In these cases, the initial purchase is not always the end of the transaction; sometimes it is only the beginning.

This is where an important economic idea emerges: some products do not work or deliver their full value on their own, but depend on other products and services that complement them.

When One Product Increases the Value of Another

Economists call these products Complementary Goods.

The idea is simple: using one product increases the need for the other or increases its usefulness.

An electric car needs charging, a printer needs ink, a coffee machine needs pods, and a gaming console needs games.

But companies have developed this relationship on a broader scale. Instead of simply selling two products that complement each other, they now build complete ecosystems that bring together hardware, software, services, accessories, and subscriptions.

That is why a customer’s value to a company may not be what they pay on the day they buy a device, but what they may spend throughout the years they use it.

The Initial Product May Not Be the Only Source of Profit

One of the best-known models associated with this idea is called the Razor-and-Blades Model.

The idea is that a company may make the core product attractive or easy to acquire, then generate recurring revenue from the things needed to use it.

The idea can be seen clearly with printers. A printer is purchased once, but ink is bought repeatedly as long as it continues to be used.

HP’s results illustrate the importance of this part of the business. In its 2025 fiscal year, revenue from printing supplies, including ink and consumables, amounted to approximately $10.9 billion.

The point is not that every company sells the device at a loss to profit from accessories; that does not apply to all products. But the example shows why spending after the initial purchase can be an essential part of the business model.

From Product to Ecosystem

With digital products, the relationship becomes broader.

Buying a phone, for example, may be a gateway to a range of services: an app store, cloud storage, digital payments, music, content, and devices linked to the same account.

Apple shows how a device user base can become a market for services. In 2025, the global average number of weekly App Store users exceeded 850 million users, while the Apple One bundle brings services such as iCloud, Apple Music, Apple TV, and Apple Arcade together in a single subscription.

Economically, the more products and services a customer uses within an ecosystem, the deeper their relationship with the company may become than simply owning a single device.

Here, the question changes from:

How many devices can the company sell?

to:

How much of the customer’s spending can the company retain after selling the device?

Convenience Itself Can Become a Reason to Stay

These ecosystems do not succeed only because customers are “forced” into them.

They often offer real benefits: devices connect easily, data moves between them, accounts, passwords, and purchases are all in one place, and users may not need to set everything up again each time.

But the same advantage can create what is known as Lock-in—a situation in which a customer becomes tied to an ecosystem and leaving it becomes more difficult over time.

This is where Switching Costs emerge.

These costs do not mean money alone. They may include the time required to transfer data, learn a different system, replace devices or accessories, and lose access to some previous services or purchases.

The UK Competition and Markets Authority studied this issue in mobile operating systems and noted that barriers to switching may include financial costs, as well as the time and effort needed to learn, along with users’ perception that the switching process itself is complicated.

Thus, as the ecosystem surrounding consumers expands, the value of staying in it may rise, but so may the cost of leaving it.

Why Do Companies Like This Model?

Selling a single product means that the company must persuade the customer to make a new purchase each time.

An ecosystem, by contrast, may give it a longer-lasting relationship with the customer.

A printer creates demand for ink, a device may generate a monthly subscription, and a platform may take a share of purchases made within it.

This means that potential revenue is linked not only to the number of new products sold, but also to the size of the existing user base and how long it continues using the products and services connected to it.

A strong ecosystem may also give a company a competitive advantage: a new competitor does not merely need to manufacture a better product; it may need to persuade consumers to give up an entire set of things they have become accustomed to using.

But Consumers Should Not Look Only at the Initial Price

This is where the way a purchase is evaluated changes.

The cheapest printer is not necessarily the cheapest over several years if its ink is expensive. And a device that seems suitable today may become more costly if it depends on subscriptions or proprietary accessories.

So the better question to ask before buying may not be:

How much does this product cost?

but:

What will I need after I buy it?

What products work with it? Is there a subscription? Can I use alternatives from other companies? And what will happen if I want to switch to a competitor later?

In this sense, the price on the shelf may be merely the price of entry into the ecosystem.

When the Product Becomes a Gateway

Complementary goods are not a new idea; cars and fuel, cameras and lenses, and printers and ink are examples that have existed for decades.

What is new is that the digital economy has made ecosystems larger and more interconnected. A single product can now open the door to a series of devices, services, subscriptions, and ongoing purchases.

This does not necessarily mean that ecosystems are bad for consumers; they may provide a simpler, more integrated experience. They may also give companies an incentive to invest in services and products that work together.

But they change the meaning of a purchasing decision.

In some markets, when you press the “Buy” button, you are not choosing only the product in front of you.

You are also choosing the ecosystem from which you may buy afterward.