Because of the potential for greater profits, power supplies with lower ratings are getting rare -- not many manufacturers that want to produce these units anymore. We talked to Silverstone not too long ago about a 300W version of their Element series. The conclusion was that the price for the production is similar to higher-end power supplies and it wouldn't make sense to build these power supplies anymore. That seems surreal when we think about the number of users that don't need more than 500W, but it appears that the minimum price for a quality power supply -- regardless of wattage -- has bottomed out at around $65. That's not to say you can't find cheaper power supplies out there, but the quality of such units is at best... suspect, as we will see shortly.Check it out over here. They tested the Antec Earthwatts 430W, Corsair 450VX, ThermalTake PurePower TR2 RX 450W and Ultra V-Series 400W.
The Ultra PSU is the cheapest from the bunch of PSUs they tested but the unit didn't perform as well as the other models which cost about 50-100% more. The overall winner is the Corsair 450VX - this product has a good efficiency, lots of connectors and low noise levels.