OsViews compared the iMac G5 to a DIY PC made from off-the-shelf parts: "The difference between these two systems is approximately $350, with the iMac coming out ahead."
Apple's base-line iMac: $1,299
DIY PC: $1,639
While this is to be expected -- buying anything piece by piece is always more expensive because it eliminates a manufacturer's volume discount -- it shows the iMac's a pretty good deal.