Looking for cheapest ardupilot mount

I am attempting to assemble a low cost quad running ardupilot. I just would like to use althold and rtl modes
What is in your opinion the cheapest (and reliable) flight controller?
I already use a rpi0+pxfmini but it is already more than 150 eur counting gps antenna and power module.
Are there reliable clones of pixracer or apm? Thanks!