I've built most of a very similar thing, for similar reasons. I recently moved the software to a CHIP instead of a Raspberry Pi, so I could buy a bunch of them

I've built most of a very similar thing, for similar reasons. I recently moved the software to a CHIP instead of a Raspberry Pi, so I could buy a bunch of them and put one or two in each room. The MXL AC404 is really expensive if you have to get more than one, though! Does anyone know of a cheaper microphone that's still somewhat decent for this purpose? (Doesn't have to be USB, audio in is ok too.)