As to cost, I'd still love to see my Quad G5 supported by a PPC NG OS.
The G5's PowerMacs are cheap right now.
And, compared to all other PPC systems I've used, this has enough power (particularly when its using an OS that supports SMP) that I don't feel disadvantaged when I switch between it and my i7 laptop.
As to legacy, I'm still not sure I'm comfortable with using parts that aren't original or retro.
After all, even with a fast FPGA installed, a legacy Amiga is still a boat anchor compared to modern hardware.
I CAN see the 'its fun' argument, but I'm not sure I want to throw too much money at this.
Neither AmigaOS nor MorphOS support SMP (at least up to now)
Regarding Vampire, it is a toy, a hobby platform for amiga enthusiasts, retro how you would call it but there are obvious many people interested to get it and those who have it are all happy about it (at least most except some active members on different forums of course). The "fun" argument is why people buy it, it is a hobby and you do a hobby to have fun. It would be different if something is for work or at least your main platform at home but that is hardly the case for most of us.