Daysleeper,
I completely agree with your assessment of how MACs are built.
As for PCs, it is much easier that 10 years ago. With all the options out there along with being 100% Upgradable of a system you build yourself, it is great fun.
As for the cheap comps you see out there, you will find a bunch of companies that are looking to sell at cost, and even below cost in order to get a name. Then there are others that are trying to make $50 to $100 per unit. (To me that is not worth my time.)
I prefer to make comps with the best parts possible in order to guarantee performance and reliability. In the long run I save a lot of money, since call backs for warranty work are extremely rare. (Businesses understand the value of not having down time too.)
Take Care,
Richard