Here's the list of components and my purchase cost in US$
Arduino atmega32u4 processor $3.82
TIP122 transistor $0.11
IRL540 mosfet $0.33
IR diode (pair) $0.11
5cmx7cm board x2 $0.52
terminal connectors (2pin) x 8 $0.45
LEDs (24 = 8x3 matrix) $0.57
resistors (various x 12) $0.30
Nextion 2.4" display $15.50
motor $0.91
MicroSD card class 10, 8GB $6.00
O-ring for drive belt $0.10
3D printed pulley pair $0.20
mount for motor $0.30
So that's all I can think of - total cost excluding BYO Nipkow disk + hub = US$30
Of course to get these prices I bought most items in buik. If you're doing a build....