(https://www.nutsvolts.com/magazine/article/turn-your-computers-sound-card-into-a-scope)
https://www.instructables.com/Oscilloscope-Arduino-Processing/
Bill of Materials: (USD conv rate on 10 Nov 2020 apply)
Probes: USD 1.34
Aux cable: USD 0.73
Breadboard: USD 1
Resistors: USD 0.13
Potentiometer: USD 0.3