Helicopter Collective for Flight Simulators are hard to make and very expensive. $1,200 seems to be a popular price for a collective. I have been developing a series of collectives that should be “kit-able” made from easy electronic components and PVC conduit and particle board. With a target price range from around $50 to around $150.
The cheapest version would be a joystick hack.
Collective_BuildLog_3B - on YouTube
The more advanced version would be an Arduino Micro project.
Collective BuildLog 5A1 - on YouTube