To be fair it’s a 5 pack

It seems to be something with a switch that disconnects one of the rings of a 4 pin. Easy enough, but $5 doesn’t seem awful.

Of course it doesn’t disconnect built in microphones, and with modern Apple phones getting rid of 3.5mm jacks it’s value is less.

At $5, most of the cost is almost certainly logistical.

From my understanding it's not just a dummy input and somehow adds noise because some computers won't pick up the input unless there's a signal.