at least on the used equipment market to my knowledge it's the other way round. Field cameras are significantly more expensive than monorail cameras. Which type of camera will suit you best largely depends on your photographic interests and your requirements in movements, bellow draw, portability and the like. For my needs the Chamonix 45N-1 turned out to fit my needs best. It's a very popular folding field camera (the iPhone of the LF-scene so to say) which shares some properties of monorail cameras.