The general consensus is that you get what you pay for when it comes to lamps.
I have bought a cheapo lamp in the past and won't do it again, but I have also bought an OEM bulb in non-OEM housing and it lasted much longer. Having said that, the longest lasting lamp was the one I bought that was 100% produced by the original manufacturer (big shock, right!).
What projector are you looking to put a new lamp into?