the price for the window will totally depend on the kind of frame you choose. 3panes (i assume 6ftx4ft) can anywhere from 800 (for halfway decent allu-frame with single glass) to 4k (double glazed, laminated, uPVC window with decent security features) and even higher.

same applies for sliding door. it all boils down to what sort of frame you want around the glass.

http://www.veka.com.my/

http://www.mqpdesign.com/

both are on the higher-end side but VEKA and AUBI are both really really good window&door solutions. i am using AUBI at the moment.