there are some rf power transistors that are in the $100.00-500.00 price range....
also take note that some RF power transistors use beryllium oxide as a package material. BeO is highly heat conductive, but very dangerous. it's dangerous if you break it, because inhaling the dust is a health hazard. aluminum oxide is much safer to work with and only slightly less heat conductive. if you buy transistors with BeO packaging, they are required to be marked with a warning label.