Hybrid cars are innately expensive to manufacture because you are manufacturing two motors, each capable of driving the car. Also, unless a battery, with its high replacement costs, is part of the system as a power reservoir, you are still forcing the primary engine to run at fractional power almost all of the time. Also, you still haven't gotten beyond the innate inefficiency of the primary gasoline engine. The hybrid is a costly interim solution with only marginal economy advantages.
If fuel availability gets to be a drastic problem, the first answer will be 70 mpg cars that are very lightweight, very aerodynamically efficient, and have very small gasoline or Diesel engines and barely adequate performance by today's standards. Think of a modern "deux cheveaux".
--two motors, interesting........ combine them. electric motor=armature spinning on a shaft inside a case that makes a field. tubine engine, similar shaped deal, just using vanes for compression. Steel is steel, copper is copper, electricity can be supplied as ya go. Make use of the wasted inertia..