Monitor prices depend on the target audience, screen size, and the features of the display. You can pick up a no-frills 22-inch or 23-inch display for $100 or less, but don't expect such a monitor ...
Currently, 1000Hz monitors seem like a distant future ... the JMGO O2S Ultra projector can project a 100-inch screen just 5.75 inches from a wall. Short-throw projectors like this are great ...