For similar specs and size, a mini PC wouldn't be much cheaper. Those that are similarly sized as the Mac Mini are generally more expensive. A Dell Studio Hybrid starts at $599 and is probably the closest PC to the Mac Mini. Shuttle mini PCs run about $500+ lightly spec'd out with a Intel Core 2 Duo proc, under $200 barebones, although they are somewhat bigger in size. Other brands run for about the same prices, a bit less if ordered with an Atom CPU instead. The Mac Mini does have better graphics than most comparable mini PCs, though (Nvidia 9400M vs. Intel GMA X3100).
The question you should really be asking is whether you want a computer running Windows or MacOS (the Mac can run Windows, but you'd have to pay extra for that privilege). Or you'd rather have something non-aluminum brick looking.
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