A couple of nugs might be typical. 1 oz is a lot of cannabis; it might take a year for a casual user to expend it. So no, your garden variety cannabis is not expensive and is comparably cheaper than alcohol, and much cheaper than pharmaceutical drugs.

"The Union" is a decent documentary about cannabis in general, including its distribution and pricing history: http://video.google.com/videoplay?docid=-9077214414651731007...