<human>:  Why is it that 3D printing is so expensive?
<bot>: 3D printing is expensive because the machines are expensive. They’re also very complicated. They need to be cooled to keep the plastic from melting. They need to be heated to keep the plastic from sticking to the machine. They need to be calibrated to make sure that the printer is printing properly. The machines are also very slow, and they require a lot of power.