When you can buy a ready-made system for $299 with multiple rebates, it's not so amazing that the average user will rush down to the retail store for a new PC.
But for the Tech or at least the technically informed, building is the only way to go.
Some time back, I took a young friend of mine to a Market Pro Computer Show here in Orlando Florida. He had $500 to spend and that was all.
He came home with all the parts needed to put together a new computer.
(and enough left over for a burger and coke)
(I supplied a few small parts he didn't have,,,drive cables, screws, etc.)
I spent about an hour with him, instructing him on assembly techniques and explaining all the pitfalls. We took it slow and easy, but after an hour, he had a running PC.
The expression on his face was "Priceless"!
I know well, the pride he felt at building his own PC. I did my first one in about 1983.
It was an IBM XT-Clone, w/64K of ram and a 20 meg Seagate HD.
If you've never done it,,,,,it's worth having a GO at it.!!!!
There have been many books written on the subject and there's a lot of help available here on the internet.
Cheers,
Andromeda43