To answer my own question (and for those that find this thread searching for the same questions):
Apparently, the production process of projector bulbs is an elaborate one. To make the product cheaper, some manufacturers take "shotcuts" causing the bulb to be either less safe, less bright or less durable or in the worst case a combination of the three. The problem is that it doesn't necessarily mean the cheaper bulb is guaranteed to be of lesser quality. Some last as long as the original bulbs and give the same quality image. But some experience catastrophic failure, like exploding inside the projector. Or they ruin your projector because they radiate heat in one direction only (while proper bulbs are made so visible light can only exit from the front, but infrared light - heat - can exit the lamp from every direction). And a lot of those cheap bulbs work fine for the first few hundred hours, then dim considerably to only 25% of the original brightness.
So, yes, you should try to avoid those bulbs.
That said, there are also 3rd party replacement lamps that do use quality bulbs made by Philips/Osram (two of the big players in manufacturing projector bulbs). Reviews of those lamps are generally quite good and prices are around 1/4th of OEM lamps. Are they as good as the original lamps? I really wouldn't know but again, looking at the reviews they at least aren't considered "cheap crap".
But (and this is a really big but), this doesn't necessarily mean that you automatically buy a quality product if it's original OEM. Apparently, these bulbs only have a limited shelf life when not used. You can only store them for a limited period of time before their quality degrades. I have no idea what happens with those lamps once they get beyond their expiration date. Are they destroyed? Are they sent back to the manufacturer? Are they refurbished? Or do they end up on the gray market? So caveat emptor. When buying an original OEM lamp from non official channels, try to find out how long these have been stored.
So to summarize, it does pay to buy cheaper lamps if you are able to verify the parts used and their age. If no indication is given about the bulb manufacturer, or if they list the bulb to be compatible with many other projectors, you should be very, very cautious.Go to the full post