Not many. Though "reasonably priced" is open to wide interpretation since camcorders can range from $50 to $50,000, something less than $2,000 *could* be considered "reasonably priced". More specific definition would provide a better response. Off the top of my head:
It's extremely hard to track model planes flying using the LCD viewer. This is true especially while zooming in. An eyepiece would make shooting fast-moving objects much easier.
Does anyone know of a reasonably priced camcorder equipped with an eyepiece?