There's a specific group of consumers that would really benefit from a sub-550W PSU. For example, I plan to build my parents a small media-based PC that shouldn't run anything more than 500W. It'll save them money, on the electricity bill, and it'll save me money on the parts. After all, they probably will not need the latest i7, or any i7 for that matter. Likewise, I plan to build myself something similar for school.
That being said, there are some fantastic low-wattage PSU out there that are capable of very high efficiency, to the point where fans are not needed! Although I am a bit biased towards Seasonic PSUs, nobody can deny that the Seasonic X-400 and X460 are both exceptional PSUs. Yes, they are expensive. However, they speak for themselves when it comes to efficiency, and you know you have a quality PSU that won't fail you (or your components).
This is a side thing, but it also benefits those who are looking for quiet. Being fanless, those two models will not make any noise. That's a big plus in my book as well.
There are other very good models; I just picked out what I believe are the best low-wattage PSUs on the market right now. As with all PSU purchases, never buy cheap PSU. That's the heart of your build, and it definitely can kill your other components if you purchase a crappy one. Do take great caution!
It's cheap not because of the looks. That only factor in a few pennies as far as manufacturing costs go. It's cheap because the components are cheap, as high-grade components are generally not used for lower wattage PSUs.