Self-made/Custom VS Branded Desktop Computers

As far as I have seen

Self-made/Custom Desktop - For those that can fix computer problems themselves and know about how to avoid overheating the computer in general.

Branded Desktop Computers - For total newbies that need the "support" provided by these companies.

Is it generally cheaper to get Self-made/Custom Desktops though?

Prebuilt systems usually come with low-rent, maxxed-out mainboards, low on ports and slots. Definitely not what you want if you're aiming for a cheap computer for now, to be upgraded in the future.

I bought a barebones kit from MagicMicro a while back, came fully assembled. All I had to do was add ram, cards, and drives. Simple tab-A slot-B shit. $350 for an Asus P4S800 board, a P4 2.6, and a big stupid black case with "Korean styling". After a bios update, I can upgrade to at least a 3.4 GHz processor. Hoorah.