This is exactly why I dismantle and inspect all 'unimaginably cheap' pieces of tech before using them for their intended purpose. That, and curiosity. There are many clever cost-cutting hacks to be learned that way.
One of my favourite youtube channels is BigClivedotcom's, where he takes apart a bunch of cheap gadgets.
Agreed.
Additionally these can be hidden in non-electrical objects with small batteries and run for weeks.