The 2014 Turbo V6/high capacity Energy Recovery System is unquestionably the most expensive F1 power unit to date.

A normally aspirated, 1,100 HP, 3.5 liter V8 (limited to 17,500 RPM) would be much less expensive to produce, and could certainly push an otherwise current generation F1 car to 230 MPH on the long straights while lasting three races (plus practice and qualifying time).

While it's true that Formula 1 has limited engine RPM and banned certain "exotic" engine materials in its later years, it important to note that such changes were implement within the larger existing formula (e.g. 2.4 liter V8s).

Today, the FIA's primary concerns are safety and giving the appearance of being "green." Those are the reasons that such an engine is banned in today's formula.