The "shadow sensor and PID feedback" they're using could be scrapped and replaced with manual control. It wouldn't be as fancy, but it would save you the $60 photodiode.

The only other sensor being used is a current sensor, a.k.a a multimeter.

You could make a real ghetto version of this jig with a laser pointer, multimeter and variable power supply.

All the laser pointer does is point at the wall and show you the position of your balance beam.