RE: How do they do it?
It's called China.
Most ARF's are made in China, (or some other pacific -rim country), and they are getting pretty darn good at it too. Don't be too impressed. They are making plenty of profit on a $70 trainer. They are made in batches of thousands at a time, warehoused and distributed through companies like Tower, Horizon, etc...
The actual cost to produce that ARF was likely less than $20 shipped.