Yes, any kind of car is wildly more difficult to build at scale than a PC. The motor and transmission are only two of about two dozen systems in a car which need to operate flawlessly.

Just the paint alone is hard to get right. Wrong alloy with wrong paint, it chips and flakes. Wrong application, it fades or scratches. Introduce new colors and they might react differently. So now you need to be a paint expert, and be a expert at applying paint, in multiple phases, for multiple parts, many times a day, and never make a mistake.

Now do that for 23 other systems in the car and try not to make a mistake. Suspension, steering, brakes, air con, heat, ECU, brake controller, headlight controller, trim fitting, interior fitting, seats, signal and tail lights, seat belts, front/side impact air bags, bumpers, crush zones, windows, speakers, stereo, main electrical / battery, alternator/inverter, wheels, tires, etc, etc. If you screw up the torque on a bolt, break a clip, forget a fitting or connection, etc, the car now has a defect and needs to be repaired or your brand suffers from consumer complaints (in the best case) or down right safety violations or injuries (worst case).

Compare that to a small metal box which has about six breadboarded electrical components, a screen and a keyboard. The car has that too, plus everything else!