Projector are getting cheaper however, replacement projector lamps are still a significant cost of ownership. The rated lamp life is the time till the lamp will be outputting only HALF of its original brightness.

There are some new Diamond Lamps which are about 10% cheaper and have the bulb from the original manufacturer who supplied the projector manufacturer. There’s more info at http://www.presentationtek.com/2008/01/09/replacement-projector-lamps-and-bulbs/