Recently, I had the good fortune of running into an old friend who I grew up with. The conversation started off casually enough until we got to my forte, computers. In the discussion he asked me what had happened to the computer market with the cost of systems now being less then 1/10 of what they used to be.
We both laughed when I told him I'd paid $3000 for an HP 500 Mghz system in 1997 that featured an 11Gb HDD. It used to be true that it had been always cheaper to build rather than purchase an off the shelf computer. After our discussion I decided to head over to Best Buy and COMPusa just to se what the retail prices were. I wasn't necessarily shocked but I was surprised that in many instances there wasn't much, if any difference at all in the cost point of a decent system.
We agreed to meet again a few days later and our discussion continued almost where we'd left off.
For the most part he was right, there wasn't much difference in buidling versus buying. Where the difference did lie however was in the quality of the components and that was resoundingly true.
The manufacturers have the benefit of quantitative buying where as we consumers don't get that benefit necessarily. A good example is computers for cars. A former local car builder in Delaware was buying the computer modules for one of their car lines for $.10, yes that's ten cents. If you had to replace the same unit in your own car it would cost you between $800 - $1100 for the exact same unit. That's an example of quantitative buying as well as contract negotiating.
We as consumers have had to forego that benefit since we don't purchase thousands of units of any particular pieces.
Over time though and with a bad economy as well as the introduction of foreign labor, the prices in the computer industry have managed to fall as the cost to produce the goods also fell incredibly. Manufacturers also became much more efficient and that is now reflected in the retail sector pricing. Along with that mix is something we all benefit from which is heavy competition. Many manufacturers building the same products with their own branding.

What is most interesting though are the parts that are used and how well or not that they work. Years ago it wasn't uncommon for someone to hold on to their store bought computer for 4-6-8 years. Now it's rare that a newly purchased computer lasts 3-4 years because of either breakdowns or advancements in the industry to make bigger and better computers on the cheap. And with the cheap cost of computers now it only makes sense to upgrade or buy new just as you would a car or truck.

The one thing that set itself apart when I was looking at the 'shelf' computers is the parts inside. The processors are the same as you or I would purchase so in that case there is no real difference. However, when it comes to the other parts, that's where things become a little more pronounced and complicated. We already know that computers, like Cheerios, can be produced by the same company but labeled differently according to the comsumers demands. A white box of Tostios versus a yellow box of Cheerios carries two different prices for the exact same product and computers are no different...or are they?
One of the biggest differences I saw was the Power Supply Units or PSU's. Many were from no name manufacturers and varied from India to Korea to even Vietnam. This in my opinion is where the 'shelf' computers fail the most. I do sidework repairing computers and it's amazing to see how poorly some of the components are actually made. The area of PSU's seems to almost be a constant but not the only issue by far. Failed motherboards are another area and one I would easily rank as number two of the most failed components. Fans are easily number 3 and one of the most critical components as well. With the cheap cost of the prebuilt computers is the sacrifice of quality in most cases. Unless you're willing to pay over $1,000 your only going to get what you pay for. In some cases you might get lucky and have a system that lasts for several years with no issues or glitches but the likelihood is diminishing quickly. Also gone are the days of calling up the manufacturer and having unlimited tech support for a year or even the life of your computer. Now you have to package up the whole system or take it to a retail facility yourself (if they even honor the warranty). Or you may get sent a part and then have to pay to have the part installed or replaced if you don't understand computers. What has been traded off here is responsibility. Responsibility for the manufacturer to stand behind their product. It's not the same in all cases but it is what we're coming to. In the higher end systems you'll likely see better service but I see that coming to an end in the near future as well.

Through out the course of our conversation I began to realize that many things had truly changed, some for the better, some not so. Overall though the one constant was that the prices had dropped dramatically over the years and we're still able to benefit from that price change. If we're smart consumers.
Again, where the difference lies is in the quality of the components.
Instead of paying $25-$30 for a good quality fan, I can now get an even better fan for $10 or even less. Instead of paying $400 for a so-so motherboard I can get a system that even NASA would be envious of for less than $200.
I can spend $400 for a store bought system or I can add $150 to that investment and have a system that is faster, better equipped and is more in line with what I need. It will stand me making a few mistakes, it will overclock 30% higher than it was made for, it will last through day after day of coding and punishing work loads. All things I most likely would not get from a store bought computer at least not for very long!

The bottom line is we can get a lot more today for tremendously less money. It is still where it's spent and how it's spent that matters the most. And although I can get a pretty fast system for less than $300, knowing how much I rely on my computer, I know that spending for top quality components is going to save me money in the long run even though I know how to change out parts and build a system. Having a computer that breaks down every so often seriously hurts me because I rely on my computer not just for entertainment and learning but also for part of my income when I'm not working construction. Reliability is in essence what we're paying for and now the cost is extremely low so quality can be had for pennies on the dollar of what it used to be.

That's not to say that a 'shelf' bought computer doesn't have it's place because it's common sense that there is a place for it. With that said, you also get what you pay for is very true, more so today than ever before.
Through modding, I've discovered what components are the best and most reliable. Which processor is going to give me the best bang for my buck. These are all things that have saved me a lot of money and also helped me to discover a new line of work that I and my customers can benefit from.

Is it cheaper to buy than build? In the immediate short term I would say yes but with a footnote.
How cheap is it if your computer is down for 3 days or a week? How cheap is it when the component that got sent to you from the factory was free but the labor is $100 - $300 to install it? These are the realities that have to be weighed out. Today though with a bad economy and many people jobless, the instant knee jerk reaction is the cheapest always, and it's understandable if you're not informed.

Being informed and staying informed is what makes all the difference.