I've heard this comment but I have not found any information about it. Is it true?
Given that alloy framed bikes are generally cheaper than CF framed bikes, it's reasonable to conclude that an alloy frame is cheaper to produce than a CF one.
There are some videos on YouTube that show the basics of the process of making a CF frame. There hundreds of individually cut sections sections of CF cloth that need to be combined together in multiple steps to give the frame strength where it is needed. All the sections of CF cloth need to be combined together in moulds by hand. This is where a lot of the cost comes from.
Cheap Carbon frames may well be cheaper to build than aluminum frames, but carbon has many more failure modes that can be introduced at manufacturing, requiring much higher levels of quality control.
It possible to buy very cheap carbon components out of China, but how many of us choose to buy these? I am happy to ride a bike made from carbon parts, but but would never consider using off brand for parts I consider critical - stems, forks, bars, frame, wheels.
Happy to use cheap carbon stem spacers though.