Low Beam Headlight keeps going out. I have replaced bulb and fuse.

I have the same problem. My local repair shop says it's cause Moister gets inside the housing unit for the headlight. There was water accumulated in the bottom. So he drilled a hole. Bt the problem is still not fixed. He also claims the whole headlight assembly costs $1500. That seems a bit steep to me. Has anyone priced the headlight unit for the halogen version of headlamps for the 2007 mitsubishi?