Raspberry Pi 4 (2-4Gb RAM)

Raspberry Pi 4 2Gb ~60$
OR
Raspberry Pi 4 2Gb ~40$

GPS modules

UBlox F9P module with USB port ~150$

GPS antennas

Helix multifrequency antenna for RTK GPS ~50$
OR
Round multifrequency antenna for RTK GPS ~50$

IMU sensors

BNO 085 IMU sensor ~20$

Analog-digital convertors (ADC)

ADS1115 ~2$

Steering Motors

DC motor 350rpm ~73$
OR
Keya BLDC with CAN-bus control

Motor drivers for DC motor

IBT-2 ~2$
OR
Cytron MD13S ~20$

Wheel angle sensors

AA-ROT-120 ~20$

CAN bus adapters (for ISOBUS connection)

USB CAN

Screens

10.1 with integrated touch ~113$
OR
Bright LCD