It depends. The only AmigaOS 4 compatible alternative is the upcoming X3500 and X5000, but they are said to cost as much or almost as much. If MorphOS is an alternative pretty much all PPC Macs with the same GHz speed are equal to the X1000, except the G5 that is faster. Except for the RadeonHD GFX cards that are a lot faster than the ones on MorphOS (though the X1000 doesn't have full 3D support yet). After that, it's only the Peg 2 left and it's slower. I should mention (before some else does it for me) that the X1000 is new and comes with warranty, unlike the alternatives.
I got a PowerMac G5 @ 2.7 GHz and a Radeon ATI X800 Gfx card (R400) which cost me about 400 euro (plus SSD, monitor, keyboard etc) and the MorphOS licence of 111 euro.
