Why Projector lamp are expensive this is because the costs to develop and make projector lamps limits competition in the market,  so the projector bubs are costly. People often get a shock when they see price of new projector lamp, expecting it to cost similar amount to a fluorescent lamp. But, however, the technologies involved are different.

Projector lamps operate at extreme temperatures and pressures, and high-grade quartz is often used to make the bulbs to ensure resistance to these stresses is achieved whilst providing a very high-quality light output. The mercury used inside the bulb is also costly, and in addition, during the manufacture of discharge lamps the bulb may be hand-blown to ensure precision.