With the new Teensy coming out, I got excited about reviving an old project, but got stuck in the same thought pattern. I am curious if there are some other approaches to what I am trying?

Basically I am trying to create a mixer for eight digital MEMS (PDM, I2S or TDM) microphones, each connected with (up to 8 core ethernet) wires of at least 30 centimeters from the microcontroller and with very limited space on their own pcbs. As far as I have figured out, the signals the microphone output, are meant to travel at maximum 10cm on a pcb itself, so some kind of boosting, serializing or balancing seems needed. However most ICs I find that do that would either add an extreme cost to the board (5 chips add up when multiplied by 8) or would take too much space on the microphone PCB.

Is there an approach to this that I am missing, or am I trying to do something that (at the moment) is not possible?