touchscreen as a tuchscreen overlay and controller or touchscreen lcd?
If you meant touchscreen overlay: the 4wire resistive would be the cheapes because they are more common (more demand->more products->lower price)
and what are you looking for? any desing in particular, small, large, self-adhesive, with glass?
usually the price expresses the product, good one goes around $100 at least (including controller- based on 10.4"size)
http://www.3m.com/3mtouchsystems/
http://whatis.techtarget.com/definit...214510,00.html