why does a generic power supplly cost lest than say an antec?

dont just say quality, specifically why is it better.

im having same issue with ram,

there isnt an answer other than quality. Quality parts cost more for a reason...cause they are better

ur avatar describes me right

In generic terms from what I understand cheaper psu's do not regulate the voltage as well as the higher quality/higher priced ones. Read this for a better understanding of psu's :
http://forum.oc-forums.com/vb/showthread.php?s=&threadid=150384

A high demand for Antec PSU's allows them to sell them for more and at a tidy profit I'm sure. Also, as with most brand name products, they charge more to help cover their advertising costs. If you're not considering an Antec, Fortron Source PSU's cost less and are highly regarded.

Edit: What kind of problems are you having with your RAM or PSU?

pc just radomly shuts off, but damn a good 300 wattter cpst about as much as ddr ram 256,that sux.

ok thats unusal i just looked it says the combined power of 3.5 and 5v volts will not exceed 245 volts. it sounds like this generic power suppply is good.i paid 20 at a pc fair.
when pc resarts it constantly says its my nvidia tnts2's fault.

Mainly quality and the output voltage. Sometimes it may be giving off less than it's advertised at.

Voltage output, and there are some safety features built into them in case they blow. Cheaper power supplies will usually discharge any remaining curent left in the capasitors through your system, unregulated. This usaully means when a cheap power supply blows, it's going to take out something/s with it. This is rarely the case with a good quality power supply.

Heat dissipation and heat tollerance...

A cheap power supply will usually have smaller, less effective heat sinks on critical components. Also, the power output of those components will drop in quantity as temperatures rise. In a low-grade psu the actual wattage produced will drop quickly as the psu temperature rises.

Capacitors...

A higher grade psu will have better line conditioning components to help keep your system stable.

Ethics in ratings...

Some manufacturers will do unreasonable tests to obtain the psu ratings such as giving you the psu output at 25C, rather than 35-40C that is more typical inside your case.