if you look back several years ago when DVD disc was first released in the consumer market, it was very expensive too. it costs $8 to $12 each. what about now, it costs only $2 each.
For DVD-5 disc, the situation is Demand > Supply years ago BUT now Demand < Supply and therefore the price drops to $2 each (very close to CD-R disc price).
Right now, the DVD-9 disc price is dropping because most DVD rewriter support DL and the demand is gaining momentum. Therefore, more manufacturers produce DVD-9 and supply is growing up. Because of mass production, the DVD-9 disc is getting cheaper.
Yes, the price will drop further, however, when HD-DVD and Blu-ray follows the history of DVD-5 then DVD-9 will become obsolete (for recordable DVD DL disc).