Are windows with multiple panes more expensive?

For Christmas, I helped my parents redecorate their living room including a flat screen television. Now I would like to help them invest in new windows. Their current windows are large with a single pane of glass. They are very drafty and I know they are letting out the heat as well as the air conditioning. I like these kind of multi-paned windows http://www.rwcnj.com/OurProducts/Windows.htm but I have never purchased them before. We have similar windows in our home but they were newly installed before we moved in. Are these type of windows typically more expensive? Also, what brand windows are affordable, attractive and durable? Thanks!