Difference in price reflects on material used mainly to be honest. Also the type of head. Some monopods will give you the option of using ballheads.
In all honesty, if you can maintain a shutter speed of 1/focal length of your lens(or faster), should eliminate any major shakes.
What you need to remember is NO support aid in the world will stop people from moving about in photos so think about other ways to keep shutter speeds up which increases sharpness. Stopping a lens also does so.
Simply using a tripod/monopod will not do the trick. Just some tips there.