Ask yourselves why there isn't more of them?
1. coaxial torque is = but you lose directional control or suffer control reversal in yaw in autorotation or low power.*
2. higher cost in main blades and controls
3. higher gearbox weight
4. Blade collision with abrupt maneuvers and limited speed unless ridged hub
More helicopter are conventional - Easier to fly - No node points in flight envelope (positive yaw control)
* See the Gyrodyne QH 50 and RON 1 - The only coaxial with positive yaw control in any flight maneuver
With a single rotor you build only one set of blades, one hub etc, A small tail rotor with it's gear box costs less.
and manufacture is about cost - mission profile - maintenance costs - parts cost. A coaxial has a higher cost to build.
If you want dual rotors try tandem like a Chinook, Wider c/g, faster, simple controls
