projector metal halide lamps

i recently priced a replacement lamp for my infocus projector and it was £350 i cant really afford that but i came across a website selling metal halide bulbs for only £12.50 and they were rated the same as my projector lamp 150 watts i was wondering if anyone knows if i could take out the bulb from my original lamp holder and just fit one of these cheap bulbs in place of the burnt out one. as it is the same type (metal halide) and 150 watt

any help appreciated

fido