It is becoming standard in latest notebooks, will be standard in new Macbooks and Macs in general, and will be feature of many Android smartphones.
Main idea is not just reduce costs, but to force you to 100% touch the sensor. Such way manufacturer will always collect lot of your fingertips and upon request (for people who have value) send them to government. Yes, without any approval and your knowing it. Such functionality is performed by special parts of modern CPUs or hubs. They also have secure storage for fingertips that you can't check.
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