I built a similar 5'x4' stand this spring for about $500. I would think you could do it for $300, depending on how fancy you wanted to make it. If you pick the right window design, and the right dimensions for drawing your bow, I would think it would be fine for bow hunting. Animals will come right up to them.
I got my elevators at Gander Mountain. They were cheaper there, plus they had free shipping.
http://www.gandermountain.com/modper...ID=4008&r=view