This is also something that's often seen in oscilloscopes. For example, many Agilent scopes can be upgraded by buying a key. The impact for users is twofold. O

This is also something that's often seen in oscilloscopes. For example, many Agilent scopes can be upgraded by buying a key. The impact for users is twofold. On the one hand users that don't upgrade still have to pay for a few (unused) components. On the other hand, if users decide they want to upgrade later on, they don't have to throw away/sell their 800$ scope or send it back to the factory. You can buy the basic model when you have the money and upgrade later. It might be a bit awkward to buy something you pretty much own already, but it's still the most rational option. If only humans were more rational...