Hehe 
They've only got G5s (20" iMacs and some towers) now, so they won't even be very good in 10 years time as Apple will have dropped support so long ago that they'll only be able to run really old OSes and software, unlike the G3 today. Can't really think what you'd want with a Mac Pro 500 GHz though - maybe if you hacked Boot Camp you could make it into a half-decent Windows 98 box? No point running OS X, giving that it would be the same as on my G3 
They've only got G5s (20" iMacs and some towers) now, so they won't even be very good in 10 years time as Apple will have dropped support so long ago that they'll only be able to run really old OSes and software, unlike the G3 today. Can't really think what you'd want with a Mac Pro 500 GHz though - maybe if you hacked Boot Camp you could make it into a half-decent Windows 98 box? No point running OS X, giving that it would be the same as on my G3