Even in the Commodore days, Amigas were considerably higher than that price for the low-end models. The only reason MorphOS is so cheap is because they're all mass-produced but obsolete second-hand models (and I mean that literally, not in a derogative sense).
Comparing Apples and Bananas again here.
No I don't think they are that much different ...
Motherboards based on say Sis 745 chipset or on Intel 945GZ chipset
are all the same even if they are produced by Asus,MSI,Epox,IBM or
anyone else ... PPC Chipsets in those old Macs are almost the same
thing as chipset used in AmigaOne x1000 ...
When you pay 3000 $ for it you are not supporting AmigaOS 4 developers , you are not supporting Trevor or Acube , you are supporting Freescale
and Varisys with that money because they will get the lion's share of
that price ...
I can see the need for having custom case,keyboard,mouse or even better having some cool piece of hardware like Catweasel or FPGA card designed
to give you Amiga experience , but I can see no rational reason why you
would want to reinvent the old Mac in the form of Amiga motherboard ...