Big electric motors are actually pretty cheap. They've existed in industry for over a century, and their manufacture is entirely automated. The raw materials cost of two motors each with half the power matches that of one motor.
The motor controllers are probably the more expensive part, although most of the cost there is engineering design cost (much of industry doesn't use fancy motor controllers needed for a car, and cars use high power MOSFETs which are rapidly evolving tech). Tesla designing them in house will eliminate much of the cost over enough volume.
The motor controllers are probably the more expensive part, although most of the cost there is engineering design cost (much of industry doesn't use fancy motor controllers needed for a car, and cars use high power MOSFETs which are rapidly evolving tech). Tesla designing them in house will eliminate much of the cost over enough volume.