I am confused by your question. There are tons of hardware stores in LA. Melrose Mac, DV Warehouse, Keycode Media. And most of the manufacturers that you see advertised here on Creative Cow are located right in Orange County, CA, just about 1 hour from Los Angeles. All more than happy to sell you excellent hardware.
But what is your real question ? Can you show up to one of these places, and buy bare bones products at rock bottom prices, and ask them "how can I put this together, now that I just have the bare parts ?". When you go to Fry's Electronic's (who has very good prices in LA), there is NO ONE there to tell you "how to do it".
If you were in NY City, and you went to B&H Photo, you would get amazing low prices, and the sales people there could not tell you "how to do it". Either you know, or you hire someone to do this for you. Or you simply go to a wonderful store, like Melrose Mac, DV Warehouse, Keycode Media, etc. in LA, and SPEND MONEY and they will help you.
So now you say "but I know that all I need are these cheap hard drives, and this cheap drive box, but I can't figure out how to get it to work - isnt' there a store I can go to that will show me how to get this to work, so I can have a wonderful RAID drive array, just like all these expensive systems, but do it really cheap ?" -
The answer is NO !!!!!!!!!! Can you go to the grocery store (like Ralphs) and ask them "I want to buy this meat, and these vegetables, can you please show me how to make a delicious meal, so I do not have to go to a fancy restaurant, and pay a chef to make an expensive meal - my family is coming over, and I cannot afford to go to this restaurant, but I know that if I come to this grocery store, I can buy the same food - can't you show me how to make it taste just as good as that chef that is charging so much money ?"