You don't need a turbine at all to do 200 mph with a r/c airplane , you can achieve it with a prop plane (see the extreme speed prop models forum) or even with a specialized glider. But nothing
beats the roar of a turbine, and yes, they are expensive. That's is a fact, and it is a motivator (at least for me) to shift to a higher gear in life.

Best rgds, Enrique