That one imac has a 3.06 ghz processor. That doesn't seem slower to me...
A 3GHz desktop processor would likely perform the same, maybe outperform it due to things like faster FSB and faster memory. You can also get faster desktop dual core processors and faster quad core processors.
Here are some reasons why someone might not have use for an iMac, Mac Mini or Apple notebook:
- Wanting to use existing display or higher quality display without waste.
- Wanting multiple identical displays.
- Wanting more than 2 displays.
- Wanting to use seperate graphics cards for windows and OSX, be it for gaming or 3D work.
- Wanting an internal RAID solution.
- Wanting more than one internal drive.
- Wanting multiple internal optical drives.
- Wanting more than 2 processing cores.
- Wanting more than 4GB of memory.
Those can be solved by going with a Mac Pro, but if you don't want the processor and memory expansion of the Mac Pro, don't need 8 cores and don't need the workstation parts there is alot of money being wasted.
A quad core Xeon 2.8GHz processor, workstation systemboard, 1KW power supply and FB-DIMM memory costs over double what you could pay for a 2.83GHz non-Xeon quad core, desktop systemboard, 500W PSU and 2GB of desktop memory. A desktop system with similar specifications to the quad core Mac Pro would cost around $1500.
When it comes down to it is nearly always about the price for people who want the midrange mac. Steve Jobs loves his iMacs though, so we will likely never see one.
Mobile components, especially processors are also expensive. Intel change $850 for a processor similar to the 3.06GHz one in the iMac, but $183 for a dual core 3.16GHz processor with faster FSB that can be overclocked well beyond that on the desktop. Obviously Apple pay alot less than $850 per processor, but if they used desktop components prices could be alot lower.