How do hotswapping computer parts work?
It requires several features, some of which put the cost up.

These include additional transient suppression on signals, which may put additional capacitance on bus signals thus requiring additional engineering/testing and may reduce performance below what's otherwise possible.

Also, connectors which longer and shorter pins that ensure that some pins mate before others and disconnect after others. This is to guarantee that signals are connected and disconnected while power and ground are already connected. In some cases, a control pin can be made to connect last and disconnect first, and this pin will tri-state all other signal pins.